Rainbow Six Vegas for the PSP is a very disappointing shooter made for it.
There a little bit of tacticalness which is hugging up on walls and it's easy to hug up on it when you don't want to and it can be annoying at some times. Another thing that's annoying when you want to open a door, but you might look through the smoke. You have to switch between two players in the game which has to help the other out or they die. The campaign will take you less than 2 hours. The multi player is pretty fun. it supports 2-4 online and ad hoc. The modes are team survival and survival and you can modify the game types.
Overall I give Vegas an average because it's just, bad. I don't really recommend you get this game because there are a lot more tactical shooters for the PSP.