Tried Assassin's Creed II and well the performance is great. I must say it's pretty similar to the earlier game. The least it drops to is 30fps with V-Sync ON, else the tearing is unbearable. It can range from 30-50fps depending on the area and I have set everything to max with AA being at 4X. The game looks identical to the 360 version for some reason. Although the 360 version seemed to have better colour patterns, which the PC version seems to be lacking right now or may be I'm just judging it too soon.
Since I have already completed this, I got it just to check the performance on my machine. My brother wanted to complete the title, so he'll enjoy the game. Guys get the game when it comes out. It's worth the trip.
Also just play Just Cause 2 demo, it's freakin' amazing. The game has totally got revamped. Everything about that game is brilliant. The graphics, physics (jaw dropping), gameplay elements, level of detail, vehicles etc. It's pure fun. The demo itself has a terrain which is super large. You have so much to do and lot of variety in it. I think I'll wait for the full game. The performance too is pretty good.