I can't fathom why this game is rated so low.
First of all, there's a plethora of weapons, and they can be upgraded. You can choose which weapons you want to upgrade, so if you tend to use a sniper rifle more than the other weapons, you can make it more powerful than the rest. As far as weapons go, you have your typical arrangement of things, like shotgun, machine gun, blasters, pistols, grenades, and different sort of launchers.
Other things that make the game fun are temporary powers, such as unlimited ammo or invisibility. The levels themselves are randomly generated and are sort of small, but I like the idea of fast progress. Huge sprawling levels are nice, but so are these sort of things, they feel right for the style of the game (has a matrix sort of feel).
The controls, well, I have no complaints. It's my first FPS that I try for the PSP, so yes, there was an adjustment as I'm used to dual analog, but I toughed it out and adapted, and now I'm very comfortable with playing the game. It has different control layouts so you can choose and then customize (to a certain extend) how the game will control, so I'm not quite sure what the big deal is.
I'm still trying to figure out why I'm so addicted to this game and why I can't put it down. It's a mix of things I guess. It's non-stop action, I like the sound and music and overall digital feel of the game. Little things like when you walk in a room for the first time, it unfolds quickly before your eyes with a sort of digitized effect, or when you blow barrels up the way they vanish.
I wouldn't categorize this as ground breaking, but it deserves more than the low rating most reviewers have given it. It's a fun game that you can play for 20-30 minutes or long sessions if you choose. You can customize how to upgrade your weapons and you have a wide selection. The boss fights are also worth mentioning as they are fun as hell. Also, randomly generated levels mean that the game will always feel different.
I don't have many complaints about this game. Only things that really bug me is that levels tend to look the same, and sometimes the frame rate can drop if you find yourself in a large room with a lot of monsters. Other than that, this is a great game and tons of fun. Good job Konami, I will definitely buy the sequel as soon as it hits the shelves this upcoming September.