Is Rachet and Clank Size Matters worth buying?

Yes I'd definitely get it. It's a great game, very similar to Up Your Arsenal in some ways, although not quite as good (probably as it was designed for the PSP). I've heard some bad things about the PS2 version so I suggest you get he PSP version, although the PS2 one would probably be ok. Now that Secret Agent Clank is out it'll probably be quite cheap as well.

This link: http://ratchet.wikia.com/wiki/Ratchet_%26_Clank:_Size_Matters might help you if you want more info but it MAY CONTAIN SPOILERS

I would get it. It's awesome, and if you're a fan of the series you'll love it. For one, you have to beat the game 3 times to get all the armor sets. The 2nd and 3rd playthroughs are relatively hard, which some people like but others might not. The weapons will take you at least 2 complete playthroughs to fully level up. For the price I'd definitely get it though.

It is really good, if you didn't play the PSP version, the PS2 version is there and it's fun. If you like the others in the series you will not find anything really different there, but it is still fun, and quite funny.

yup

YESSSSSSS IT IS AWESOME

no really. although it is fun(I played and finished it ) it's short and you can try to download it