What do you get when you put 10lb of game into a 5lb bag?
The voice acting was pretty good, as well as the graphics and animation (considering the PSP's limitations, of course). The world seemed a little empty, which they tried to explain in game (everyone's indoors because of the Templar's oppression or something), but after the living world in AC1, it is a little disappointing. I also miss some of the stealth elements from AC1...this is more of a straight up hack and slash, with a few rooftop runs thrown in. Hitting an unsuspecting guard with a throwing knife is still satisfying, though, and nailing a guard with my hidden blade and then walking off while he staggers and falls is still awesome. I just wish every mission didn't end in a straight up fight, rather than sneaking around and figuring out how sneak in and out.
If you liked AC 1, you'll probably like Bloodlines, even if it's just for the nostalgia. Otherwise, well, I wouldn't promise that it'll be in your top 10.