Buy it.

Well, buy the first three for the PS2. Ratchet and Clank, Going Commando, and Up your Arsenol (specially UYA) kick ultimate ass, are cheap to buy, and are hardcore. The fourth PS2 game, Deadlocked, isn't as fun.

Don't get the PSP version, the controls suck.

If you have a PS3, a new version is coming out soon.

Seriously. Shoot things. Good game. Exploding sheep.