First and most important of all: it's fun to play.
The roster is quite large for a PSP game with 15 initial characters that come from both Fate Stay Night and its sequel Hollow Ataraxia.
There are different things to do in the game: fight against another player, against the CPU, do missions for each character or fight in the arcade (8 fights one after the other); my favourite section was the arcade which loosely follows the different routes of Fate Stay Night and Fate Hollow Ataraxia and the stories each character has (for example, playing as Saber has Gilgamesh as the last fighter). Beating the Arcade mode will unlock different stuff such as different announcer voices, illustrations, cut scenes and the 3D model of the character you beat the mode as to look.
It's easy to play, fun to master, although the difference between the characters could be better done; while they have different designs and abilities (for example some can shoot projectiles), the combos are practically the same for all characters, which means the same combination of buttons that makes Saber do a super can be exactly replicated when you choose other characters like Archer. Hats off for characters like Bazett and especially Sakura who play way differently than other characters (Sakura is very slow but long range and her patterns are very different from the rest).
The art for both the illustrations and the characters is very good and, being a game from 2009, done with the classic art style (so pre-ufotable); the models are surprisingly good for a PSP game and you can actually look at them in the Extra section (also I have no clue why but Sakura has some very distracting jiggle physics she seems to be the only one to have them).

Overall a solid fighter with not bad music, great voice-over and fine backgrounds, not as deep as it could be but then again I did not get it for the fighting experience but to see Fate characters beating each other up.