I got it. Amazing graphics and effects. I was in awe with the whole look and how alive the whole place is [i love the medieval/crusades theme]. The areas are huge [GTA effect], multiple cities and requiring quite lengthy horse rides between cities.
Just the amazing size and look of it all will keep you busy till the 3rd-4th assassination.
After that, it gets a bit too much of the same routine [grab your horse, gallop all the way to the specific city, save a few citizens, pickpocket, climb lookout points, find the assassin HQ, do the big kill..next] . There's alot of side stuff there too, i haven't figured out what exactly i get for doing it, [i.e like all the flags in hidden places you collect] . But sadly it doesnt' change. Take GTA and imagine having the exact same 4 missions in every area you "unlock" and then doing these same 4 multiple times [i.e save 10 citizens...find 12 lookout points...].
Anyhow if i can sum the game up :
Take Prince of Persia's gameplay [climbing/running/combat] and Grand Theft Autos environment/explore/mission mechanism, dumb both down and you got Assassin's Creed.
Still amazing fun i'd say. I bought it, and i still think it was worth it. I'm specifically thinking of other games i got recently, like Hellgate:London ....now THAT was a waste. I spent more time in Assassin's Creed sitting on top of lookout point staring at the city of Jerusalem than playing Hellgate....
At the very least AC is awesome for showing off your PC graphics

.
If you haven't played it before, i'd say get it. If you already got/played it on a console...do not bother. The PC version doesn't bring anything new to the table.