I was disappointed.. More like GT3.5.. The AI still is incredibly bad..
If you want an actual racing sim, for the PC, check out
GTR - FIA GT Racingyou can download the demo on that page..
The graphics are okay (IMO, better than GT4 simply cause of the higher rez and AA and ANIS i have with my vid card) Actually I take that back, they are great, but miss some latest and greatest effects.. But little details and realism this game is suppsidly unheard of. The physics engine and modeling is incredible.. They have actual MOTEC telemetry data to model the car.. then got actual drivers of the car to test it and sign off on the realism! I don't think no other sim game as gone to that depth.
Hell, the gameitself even spits out MOTEC data files, and you open the actual MOTEC analyzer tool to look at your car data!!!
This game has pretty good electronic music too for the menu's and stuff.

With a logitech Drivier Force Pro (get rev

and the beta 4.60 Logi drivers its pretty wild. The Force Feedback is awesome.. GT4 doesn't even hold a candle to it (with the DFP too)
people go crazy with all assorted high end interface hardware..
Also, they have lots of online play and online leagues...
Its incrediblly fun to have a _clean_ race with people online.
Unfortuantly, you have to order overseas to get a copy here in the US... I got mine preordered.... total cost incluidng shipping is $50 USD... so its not unreasonable.