Joining the tracks can be difficult. You can also use another depot to turn the metro train, or build looped lines to avoid building the small loop at the end. Large loops are much easier to make in my opinion.
Can we have something like "shunting tracks"? It could be an object (not a spline), that would have 2 or 4 metro tracks on which the trains could reverse (using a waypoint) and drive their way back on the line. We would also LOVE to see all metro trains actually have driver cabs on both ends, like in real life. That train with a dead end seems odd to me.
The large map size means there are bottlenecks in cities, that could eventually clog the whole road system, so there is a moderate amount of cars in each city to avoid this.
I think that most of us here would love a patch that added a lot more live in our cities and a bigger challenge for public transport. I can build tunnels, overpasses, everything - but all this seems useless, since there aren't many traffic jams (up to now, I only noticed one single place where a jam can create). Many people complained about the jams in CiM1 - but that was because the vehicles were getting stuck in a stupid way. CiM2 has to fix that, and I think you need to improve the overtaking and lane selection mechanism, along with better traffic. (By lane selection mechanism I mean that many cars can still get stuck in a stupid way, and buses don't use the bus lanes for turning left, as they should.)
"4. Although definitely not a showstopper, I too am interested to see why things like train lines and airports have been removed from the game. For me, in CiM1, they were very reliable starting points in that I knew that they would always attract a decent number of passengers to get my lines started. Additionally, some kind of connection to the "outer world", although abstract, would just add to the realism of the game."
These are all good ideas and we will keep them in store! Right now we are concentrating on making all the fixes as fast as we can, but we would like to add more to the game later on.
I hope for the heavy rail and airports too, probably we could build them in the map editor, or mark some special space for them, so that they get generated when there are more and more people moving into our city. The terrain around the planned railways and airports could be locked, so that there is no problem with actually placing them with the game engine. We could have like 2 different types of railway stations (but no dead-end stations, they aren't as popular as the pass-through stations), small and bigger, and 2 different airports. The latter could be build in such way: place the main building connected with an ATC tower, place the runway (single object) and connect both ends of the runway to the apron (multiple runways should be possible, although up to 3 for a map could be a good limit).