Well, what can I say, it's looking amazingly impressive and pushing the PlayStation 2 a lot further then I thought possible.
UK car magazine Evo had an 8 page spread on the driving sim legend himself, Kazunori Yamauchi, they caught up with him at the recent UK Millbrook testing event. According to Yamauchi-san, the lap times in Gran Turismo 4 will be remarkably similar to what would be achievable in real life :O
If you look carefully at screenshot 6, there's a snippet of text which has been cut off from the scan. It says:
Wow! PlayStation 3 handling this at a breeze anyone?
News source: GT4:UI
Screenshot: Possible render (looks too good)
Screenshot: Corvette in the city
Screenshot: Replay at the Tsukuba circuit
Screenshot: Suburu in what could be the Grand Canyon
Screenshot: Look at the detail!