Story: As with all GOW entries, Kratos's actions alter Greek mythology enough to make it entertaining, and it is always interesting to see how they integrate Kratos into the mythology. The only problem is I can't help but feel the story is tacked onto the series. Especially given Kratos's emotions in the game, it seems that the occurrences in Ghost of Sparta would have played a larger role in later entries (GOW 2 & 3).
Gameplay: Its pretty much the same as all other entries, so you know what to expect. Melee combat is fluid and responsive. A weapon received later adds some variety although I haven't experimented much with it. There are only two real complaints I have. First, magic attacks are not integrated fluidly into the gameplay. Given that magic is mapped to the directional buttons, you have to take your thumb off the analog stick to activate the magic. Second, the enemy placement gets kind of stale. While there are instances where different varieties of enemies are thrown at you at the same time, you are usually fighting similar waves of enemies.
Overall: It was entertaining and technically impressive, especially given that it is on the PSP. I don' t think it adds much to the series though. I would give it a mid to high B. While I think one needs to be caerful when comparing the console versions to the handheld versions, I don't think Ghost of Sparta stands up to the standards set by the other entries. The story is just too weakly integrated into the main story, and the gameplay is slightly less fluid. That said, its still better than almost anything else on the PSP in terms of action gaming.