Considering the constraints of the PSP, this is a pretty good game.
Strengths:
Graphics: For a PSP game, the graphics of this game are really quite good.
Controls: For the most part, the controls are very smooth, pretty much like those of the original game.
Weaknesses:
Length: This game flew by QUICK. I finished it in two sittings, you can probably do it in one.
Audio: They recycled the same audio from the original game, which while good in itself, has gotten a bit old at this point. Also, the voice overs were disappointing. They didn't get the same voice-actor for Altair. This time, he has a (fake) Arabic accent. It really threw me off the first time I heard it, and it's hard to get used to.
Character Models: This bothered me because the character models, especially that of Altair, aren't very good. Not that the graphics themselves are bad, just that the proportions seem to be off from those of the original game.
Overall:
Good game, well worth playing. Short, but expands on Altair's storyline, and adds on some more mysteries. Really, the storyline should keep you going if nothing else.