I know this is a bit late, but I feel like it's still topic-worthy.
I'm actually kind of glad that terrain is being taken out.  It will force people to create bigger and better builds.  We won't have "Slope TDM's" with a box on either side of the mountain range and have that pass for a server.  People can strategically build the terrain to suit the needs of the server exactly.  imo, it will make for a much better server experience.
Now onto vehicles.  We all know that currently the vehicles are pretty bad when it comes to driving on nonflat bricks.  When a hill is built, most people tend to use either bricks or plates.  Now, asking for vehicles to drive smoothly over bricks is just plain stupid, but I think that we really do need the vehicles to drive well over a slope made of plates.  Vehicles will have to be updated in V22.
Anyway, that's my rant.  Opinions?  Anything to add?