I'll speak only for me.
I play in windowed mode 1024x768 because I'm still beta testing, and it is easier to go back to my documents. For my own pleasure I would use the normal resolution of my screen that is higher of course, no longer with the grainy aspect of EU2. The screen being bigger, I see more terrain at a time.
I'm alternating english and french, classic and modern font and also something related to a secret project without leaving the game or modifying the settings.txt. Much easier to test. Of course, when a classic gamer has chosen a settings no need to change every day, but it is available.
I've no time to lose, as I'm testing. So all the notifiers come usefully. They remind me to change my domestic policies, a truce expired or whatever is important and I might forget. I'm not yet use to the pause with F9 as I've already a pause button. But the zoom with the wheel of the mouse is priceless.
I'm better informed by all the tooltips. the effects of the events are readily available. I've a lot economic or military info without refering to the ledger, all hovering the mouse on objects.
Well sprites are fun, but I'm a no-nonsense guy so graphical gimmicks wont impress me. there are a lot, they are pretty, the game is better with them then with the old one but for me that's all.
I've not had time to play seriously yet. I'd like to try some of the available mods. Maybe not AGCEEP, I'm not a fan of the 10000 events, but maybe some in early medieval times, they seem to have big potential for fun. I think there will be more than ever, and it is also thanks to the changes in this game from what eU2 was.
Lastly, and it is a personal view, I've spent hours on EU2, If i was to spend 20€ more, that wouldn't pay the pleasure I already had. Actually, It would only pay part of the hours already spent.
I already wrote something about old and new here :
http://forum.paradoxplaza.com/forum/showthread.php?t=442019
And I’ve posted what was published on the new features of the game in the FAQ