I haven't played Trackmania since the like 4 hours I tried TMNF, as I'm an old school TMSX player. I actually still have a super nice WinXP Machine that I play TMSX on from time to time since it won't work (easily) on Vista or newer OS's without some ... "tricks"

One of my favorite parts of Trackmania was not only the level of customizing tracks, but custom cars. I get we can do graphics on our cars, but what if I wanna drive around in a VW Golf or Mazda RX8?

Will that not be possible in this version of Trackmania? Kind of a downer if so

No, custom models aren't really supported in this game.

I have to say, it makes for a much more consistent and enjoyable experience online. You don't have to worry about someone randomly joining with the Eiffel Tower or some other annoying custom car model and ruining the experience of others.