I also just rented the game, it seems pretty cool and I like how it has more than WRC cars on this one, but overall the game seems pretty much the same as CMR 03 (graphics and gameplay wise), not that theres anything wrong with that. I'm gonna have to practice a little more before i can start attacking the career mode, but the game is still pretty easy to just pick up and play.
"It's the only car I've ever driven that'll spin the wheels at 200 mph."
-Mark Donohue, talking about the Penske 917/30 twin-turbo Porsche Can-Am car.