A fun little game with a few flaws.
The story is interesting, and qualifies as unique. The action is fast and challenging enough to give players a sense of accomplishment when they beat a level. If you want to compare it to other games you've played, this is best described as a cartoony Devil May Cry.
The game offers multiple levels which all stand out visually. The lack of repetative environments is a nice change for a shooter.
Loads of unlockable weapons, which are purchased with "widgets" also add to the fun. The different weapons have different abilities are are better used against certain bosses. This adds an element of strategy that is also missing from a lot of shooters.
The only flaw I see in the game is camera and control. Yes, this game would benefit from the two stick dual shock control, but that's just not an option. I think a lot of people have gotten spoiled to the dual shock and thus have a hard time adjusting to the more simplified PSP control system.
Overall, I think this game is a great addition to the PSP library and hope to see more original games of this nature appear on the system. It has a few flaws, but does a good job for an early release for the system. An enjoyable experience and worthy of purchase for PSP owners.