Had a go with the 'vette (and racing version), RX8, Saleen, F430, Porsche, Mustang & M3 - all assists off
Firstly, never played Forza 1 - so my first impressions are pretty good. Visuals are very slick, no doubt about that. The replays are nicer but then again it's 30fps, which to be honest I could live with for the extra detail, but hey ho. Car models are very nice indeed, and it's even better when they're roughed up a bit too! Although as was said before the brake disc glowing could be toned down a touch.
The cars sound awesome, the 'rarri especially, very throaty exhaust note which sends shivers down my spine

The other cars around you sound spot on, really gives you a sense of 'i'm driving for my life' and right in the thick of it!
I'm no expert at driving games but I like the handling, every car has very different characteristics. In the Porsche you can chuck it around like no-one's business and still stay on the track but in the F430 you have to be very careful (but have the back end out lots hehe). And the Race class cars.....well.....

I've started as I mean to go on and have all the assists off, and it's very raw. Braking on the pad is particular and a bit too much and you'll lock right up - but it's very satisfying indeed.
There's more points I could touch on but won't (want to play!!!), but all in all I think it's far more 'involving' than say PGR3 (even though it's an arcade racer). You feel more enthralled and 'in' the race. Don't quite know how to put it...but it's very good
Tom