Black Rock Shooter's excellent presentation and gameplay more than make up for its slightly dated graphics.
One thing that deserves a lot of appreciation is the game's presentation. Unlike some other action RPGs on the PSP, Black Rock Shooter is a cutscene-filled, fully voiced game. All the cutscenes are shown in the game's engine, except for a few voiced image cutscenes (similar to Metal Gear Solid: Peace Walker's), and the cutscenes are brilliantly animated. In fact, one could go on and on about the animations in this game, because they are excellent, whether it's the cutscenes or the skills used in battles. The camera controls are good, too.
The game doesn't share the universe of the anime. In fact, Black Rock Shooter here is a whole different character. Humanity is dying out after an alien invasion, so half-human, half-machine weapons called Grays are built to combat the aliens. But when Black Rock Shooter, a Gray more unique and powerful compared to all the others, is awakened there are only twelve humans left on earth. The game's story is very good and BRS's character development from a mere weapon who can't even figure out who her allies and enemies are to a really human character is well done.
The graphics are a little dated. While the animations are, to reiterate, outstanding, the character models are a little jaggy and up close, a little drab. Still, they are competent enough to get the job done. BRS and the antagonists look good, but nothing will blow you away in the graphics department. The soundtrack is excellent. The voices aren't in English - they are in Japanese, with English subtitles. Perhaps NIS America realized that it would be Japanophiles who would buy this game even now. The sound effects are good as well.
The gameplay is perhaps the closest the PSP will ever get to a light gun game. The non-combat sections are like Crisis Core: Final Fantasy VII's - you run around with the analog stick, control the camera with the L and R buttons, and press Triangle to open the menu. There are terminals which allow you to save and refill your health. The battles resemble light gun games somewhat - you move your targeting reticle over enemies, press Square to fire. But it's not all light gun here. You press R and one of the face buttons to use one of the brilliantly animated skills, and L to access your items. You press Circle to dodge and X to guard. You can't get too trigger-happy though - dodging and shooting will increase BRS's heat level, and she'll overheat if you don't pause in between shots. Normal battles are somewhat challenging, while boss battles will punish those who think they can make it without ever guarding or dodging, or those who save their items for later even when they need them. There are bike missions as well, in which BRS can destroy enemies by swerving to their side just before colliding with them. One she destroys enough enemies she can use the bike's machine gun.
There are Challenges which when completed, unlock extra skills or items for your use. At the end of each chapter, you unlock a Free Hunt mission, where you go through the whole chapter, defeat the chapter boss at the end and unlock everything related to that chapter.
Overall, Black Rock Shooter is an excellent PSP game. It has that certain endearing quality of early PS2 games. It should take you around 8 hours to beat the game's main story, but the challenges and extra missions should keep you going for a while after that.