I had it for a bit but didn't play to much as the AI was pretty much the same every race, zoom off and you catch them up on the last lap and take first.
Didn't seem to have the playability as GT5 in my opinion but I didn't give it a good blast like I did on GT5.
I think there is still a lot of players online but the grind put me off with getting currency for new cars, just took forever.
Traded it in a few days ago.