Blim invited me yesterday so I could have a hand-on. I can't answer all your questions but here's what I can say:

1) There's a little bit of pop up in the distance sometimes like on trees for example (or in the crowd in the stand) but it's really something you don't really pay attention to once at the wheel.

2) I didn't watch any of the replays so I can't tell you about that.

3) I didn't play all the available tracks but I'd say it depends on what you want from the game. The number of cars and the different handling help break the routine I'd say. Also, it is a game where you need to know the tracks well enough so in the end you need to practise, hence, drive on one and the same track to improve. IMO though, some of the really short tracks are quite unnecessary and I wish there were more different environments especially since some of them like NY look terrible due to awful lighting. :(

4) I'll let Blim answer that one, I only played arcade mode and time attack. :)

5) Though the graphics aren't that impressive (pretty so so to me though the Nüburing has never looked that good in a game), the game is just awesome because of the great physics. It's really a blast to play with the wheel, there are so many cars available it's hard to make a choice. The animation is perfectly smooth and the game just makes you want to play more and more. It was actually difficult to get Blim to give me the wheel once in a while if you see what I mean. ;) So basically, I found Forza 2 really promising in terms of driving sensations and that's really the bottom line, isn't it? :)

I played on Blim's huge HDTV. As I said, except for some slight pop up in the distance, I didn't see that many jaggies in the preview. As for the aliasing, it's there alright and it's more or less noticeable depending on the tracks. But you tend to forget about it when driving, it didn't bother me that much anyway.

Now when it comes to comparing Forza to PGR3, it's not that easy to do... As I said in the comment on left on the French forums, I wasn't blown away by the graphics and having played PGR3 the day before, I have to say it's not that bad compared to Forza. I'd say Forza just has PGR3+ visuals so to speak but again it really depends on the tracks. The Ring really looks better but New York is to me horrible because of the unrealistic colors and lighting. So basically Forza isn't the game you're going to show for its impressive visuals but it definitely looks better in motion.

Obviously, this is just my opinion so the best is to wait for the demo to be released so you all can see what the fuss is all about. ;)
Let me get things straight though, the gameplay really rocks and I can't say the game is ugly at all, it's just below my expectations that's all. :)

Well to me, the colors and the lighting suck and are in no way realistic on that track. ;)

As I said, it's just my opinion. ^^

My bad, so Forza definitely wins, I mean fewer jaggies than in PGR. From what I've seen anyway. :)