Some random thoughts that didn't make it into the preview:
1) Did anyone notice the Templars having land in Italy in one of the screenshots? Did anyone stop and think how that happened? They didn't conquer it. I did (as king of Castile, Aragon, Galicia, Navarra, Venice, Africa, etc.). The Turks conquered Beneveto in Italy and I took it back. But, since I didn't feel like running it all, I granted the entire duchy (holdings and titles) to the Templars. I got a nice pile of piety, and they got an independent bit of land. They are not part of my kingdom (although I can generate claims on them and annex them if I were so inclined, which I'm not). This is a nice mechanic, because no one would want to just grant land to the Templars and turn them into a perma-vassal (which would be stupid), but it is nice to be able to grant them lands to make both the Templars and the Pope happy.
2) In a recent patch, the AI learned how to excommunicate. This has made the game much more interesting, and that anti-pope mechanic is looking mighty attractive for Roman Catholics.
3) As you know, the game supports tyranny-like mechanics from EU:Rome. In CK2. you can try to imprison people you don't like, but doing so penalizes your relations with all vassals. It's more complicated, though, than EU:Rome. There are legitimate reasons to imprison people. If the character fulfills one of the following conditions, imprisoning is free: leader of a plot you know about, kinslayer, has acted dishonorably to you (tried to assassinate), just lost an independence war against you, via event, and excommunicated. This means that sometimes it behooves you to refrain from acting against political enemies until they make a mistake.

Also, imprisoning is not 100% foolproof. They can get away and either flee somewhere else or rise up in revolt. One of the things your marshal does is go on a mission to increase the chance of successful imprisonment.
4) Once a character is imprisoned, you can execute them, banish and confiscate their titles, ransom them, or release them. Yes, you can even "ransom" your own vassals, simulating historical events where the king would win and demand cash from defeated rebel vassals. However, aside from ransom and release, all punishments carry with them tyranny penalties. Execution results in the heir inheriting, so the tyranny penalty is light. Banish and confiscation has a much higher tyranny penalty based on the number and kinds of titles they hold. Banish and confiscation against powerful vassals will trash your relationship with your other vassals, but will either enrich you OR you can give those titles out to loyal people who, despite the tyranny penalty, will love you because you made them a duke. Even worse, though, is that the banished person still has claims, so they can find refuge at another court and that liege might DOW you to back their claims. Decisions, decisions...
5) Executing close family will make you a kinslayer just like assassinating them does. You can't game the lawful imprisonment system to secure inheritances without everyone seeing you for what you are. For example, I imprisoned and executed my scheming brother last night; I was his heir, so I got two duchies out of the deal. And he was plotting to kill me (I was his heir and he was my heir because were still young and heirless). But executing him made me a kinslayer, so pretty much the whole dynasty hated my guts. (This ruler was also syphilitic, hunchbacked, and gluttonous, so his wives all hated him, too.

) This also means that sometimes it is better to just let family members rot in prison for decades on end than it is to get rid of them. At least in prison they can't get up to any mischief, and you don't have to piss of the rest of the family by being a kinslayer. It always makes the holidays awkward when you executed Uncle Harald for trying to murder you.
6) Every time you win a siege, you gain a small amount of cash to represent pillage. It's not a lot, but it can help keep your treasury in the black when times are tough.
7) Every time you win a siege against heathens, you gain some piety. Even if you don't "win" the crusade and get full credit, you can boost your standing with the church by supporting it.
8) The three different holdings in the game serve different purposes. Castle holdings generate nice levies, have nice fortifications, and low tax revenue. Bishop holdings have decent taxes and decent levies. City holdings are the cash cows of CK2. Their levies are crap (as far as I'm concerned) but they generate more than twice the revenue of a castle holding. Of course, you, as a feudal ruler, get a huge penalty to ruling a city directly, but you can give it to a vassal and still get more money in taxes from the mayor than you can get from ruling it yourself.
8) You can create republic vassals if you so choose. If you annex a swath of holdings, you can grant the mayor of a city holding the country capital (no matter what kind of holding it is) and he becomes a count-level mayor (lord mayor in most cultures). If you grant him a duchy, he becomes a duke-level mayor (a Doge, usually). And since city vassals operate according to city laws, you can generate a decent amount of tax revenue from your republic vassal. Conquering Venice and Genoa, and then just letting them remain republics while you skim taxes off the top is quote possible.
9) Anti-Popes serve a defensive and offensive purpose. Defensively, if you have an anti-pope, you can ward off excommunication AND invasion CBs. Offensively, you can push your anti-pope's claim to the Papacy and make them Pope if you are successful, giving yourself a loyal Pope to do your evil bidding. In competitive multi-player, if everyone are playing Catholics, you really need to monitor the religious screen and your messages. If a human player backs an anti-pope, you either need to strike them down OR back your own anti-pope. Otherwise, the Church will be used against you effectively and with great frequency.
10) At the moment, heretics within the same faith get a holy war CB against each other, just like the holy war CB that Christians get on non-Christians. That means that if a ruler embraces Cathar or Lollardy and you are a Catholic, they can invade you with impunity AND you can invade them with impunity.
11) I don't want to hear anyone complaining about historical inaccuracy if they start prior to William conquering England. Why? Because if William fails to win the war, England and France never enter into their centuries long rivalry in the west because France has no claim to English lands on the continent (there is no real fuel for conflict if the Anglo-Saxons win). Without English counter-balance to French power on the continent, France has a free hand and enough manpower to do a bunch of other stuff, like get involved in the Reconquista or southern Italy. If the Norwegians win, then the balance of power is even more screwed up because Norway has enough manpower and cash to dominate everything north of Holstein with English lands backing them. So, in short, if you want a recognizable political landscape, start the game AFTER William wins. Otherwise, you end up in literally a totally different medieval world. (Which I actually like; however, everything you know about medieval politics and foreign policy is more or less wrong if William loses the war.)
12) Being a vassal in CK2 is much more fun than CK1. I spent 250 years in one game as a vassal of the HRE and had a load of fun. If your crown laws are really low, vassals can fight one another, start their own wars against enemies, and generally do what they want, short of attacking their liege directly. So, as Provence, I spent my time annexing my neighbors (and Genoa), going on Crusade, annexing North Africa when there wasn't a crusade, and generally being a powerful guy. My ruler was eventually a king 6 times over before the game ended due to a new patch. And I was still a vassal because the Emperor can have king vassals. It only stopped being fun when the crown law passed that made it impossible to fight other vassals anymore. Then I started scheming to get rid of my liege.
13) I had a great game as Anglo-Saxon England. But within 50 years, my ruling dynasty was Italian (we were still the descendents of Harold Godwinson, we just spoke Italian). And after another 50 years, London, Kent, and Wessex were Italian, too. Then my heir got tutored by an Abyssinian Monophysite (the former Queen mother). He became a monophysite, and since we was a brilliant diplomat, most of his vassals followed suit. It took 200 years, but England had become the land of Italian Orthodox heretics. Interestingly, the Irish and Welsh counties embraced it sooner than the Scots and Italian counties.
14) In case you didn't know, all (or most) titles have Christian and non-Christian appearances. You can't see it in the Golden Horde screenshot, but all the icons for the Anatolian titles are Islamic in symbolism. If they were owned by Christians, they would have a different appearance. It's twice the artwork, but it's well worth it to prevent odd things.
15) I don't know who at Paradox decided to hire Andreas Waldetoft to do the music for CK2, and I don't know what they paid him, but it is best idea and investment they made for this game. The 24 song soundtrack is so good, it's getting copied into my music folder to be played at non-CK2 times. If Johan or one of the other Devs is hanging around this thread, tell Andreas that he gets a gold star for his soundtrack. It's even better than Vic2, and I liked that one, too. However, would you ask Andreas if the track
In Taberna is related to the Latin folk song In Taberna, which is basically a Latin drinking song?