I bought this last night and have spent about 6 hours with it so far.
Mostly, I like it. I like the FFB, and it's nice to have a lively front end. I particularly like the feel of the GT-R. Some cars are a real challenge to drive, and it can feel like RBR if I'm being particularly clumsy
However, the game is obviously nowhere near being finished.
First impressions weren't good. The GTRs looked like they were covered and mud and the entire colour pallette was really washed out. I maxed all the graphics settings and that helped.
I then tried a Clio race at Lime Rock and it was like someone was releasing a smoke bomb an the tight double apex bend. Every lap there was excessive smoke from ai lock-ups.
I downloaded the Mills Metro course and the shadows there are crazy. There is a huge black rectangle that obscures part of the view nearly all the way around. I had to turn shadows off.
While those are bearable, the killer for me is the lack of performance. There is quite a lot of micro stutter on certain bends which I can't shift. Initially, I had vsych off like nearly every other racing game but this produced stutter and jerky movements. Video v-synch helped remove some of the jerkiness but not the stutter. I'm now running with D3Doverrider with triple buffer v-synch but the stutter still won't go. Fraps records 60fps constantly with the rare drop to 57 or so but it's obviously not running a smooth 60fps. I turned a few graphic options down but that made no difference so I'm back at most things maxed (apart from shadows). I have a 3570k (@4.2 GHz) and a 7850 so my PC should be ok. I'm on Catalyst 13.3 (I think).
So, in summary, I can see the potential with this game and what works, works really well. Its handling makes all my other games feel a bit sterile. But, I've spent £30 which is double GSC2012 (as an example) and I don't think it's earned the right to be sold at this price considering the state it is in at the moment. Unless I can get the stutter sorted, I will probably get a refund and come back and look at in 12 months time, or wait until someone like Reiza use it.
Also, do ISI host the online servers?