I Seems that the PC version of Assasins Creed has some major compatability issues with lots of people not being able to install. I had this problem too but i managed to get around it by using my secondary DVD drive (not sure how this worked, but it did!)
This game (On the highest settings) is much better graphically than the PS3 version, the loading times are considerably shorter than the consoles and the controls (which i was worried about) were very easy to use and re configure.
I would reccomend this game if you really enjoyed the console versions or if you havent played the the console version and are looking for a solid game.
The PC version isnt for you however, if you did not enjoy the console version or if you bore easily. The missions become repetative (even with the new missions on the PC version).
On the whole, Assasins Creed is a good game, and a good port from the consoles.........if you can get it to install. ;)