i have that game as well...
i really liked the online features of the game, like running around the island with your friends, just cruising around
another thing i really liked was that this is one of those few racing games that lets you drive a stick shift with clutch and everything
i actually made myself a little gearbox out of some joystick parts and a USB mini keyboard, plus a clutch pedal, so i could 'sim' it better
check it out
here (never mind the different name... i use that one when HarvesteR is not available on forums)
oh and yes, the Audi TT is the bes starter car... although i think the saturn is much nicer-looking
my favorite car in this game is the Aston Vantage V8, i don't know why... it's not really the fastest or best handling car out there... i just really like it... i think the fast cars are too insane to handle when you're not racing, especially that Saleen S7 which is just on the cusp of being uncontrollable (you have to start it on 3rd gear to avoid a powerslide, and never go below it)
Cheers
HarvesteR