Bloodlines is a good game. Not great, but not bad.
Graphics are stunning. One of the best looking games on the PSP.
Controls are meh. The climbing feels good, but jumping is horrible. "Jump" and "Drop" are tied to the same button, so you need to have perfect timing to pull off a jump, ruining rooftop runs. Also, moving the camera disables the action buttons(not a glitch, just the way the controls were set up). UPDATE: I realized that you can actually hold the x button to jump, but they never tell you that.
Anyone who has played AC1 knows it is crazy repetitive. Fortunately, Bloodlines (kind of) fixes this. Where you had to synchronize with maybe 10 towers in one city, now you need to do 1 in each level, every city being broken up into 3 or 4 levels.
However, there is a focus on action in this game. AC1 was about doing boring 20 pickpockets, synchronizations, eaves droppings, and interrogations to assassinate one person. Bloodlines is about hacking your way to your target. There is very little stealth, and you are forced to fight the same battles against the same enemies over and over. Even worse, nearby guards run to your fight, pitting you against many(I once had to fight 8) enemies at the same time. Counter kills are one hit kills, but require surgical precision and often make fight boring with the same exact kill done maybe 5 times in a row.
Bloodlines is like a steak that has been cooked well, but has no sauce or side orders to be eaten with. It is a basic action game, enjoyable but not worth 40 bucks.