Matsu x
How was Portable? It looked interesting, though I don't have a PSP to play it on.
In my opinion it's worth it (especially if you have a friend with the same game=special missions in multi-mode)It would be much better if it had an infrastructure mode though.
PS, my favorite grenade would have to be the robo-pitch >.<
http://www.youtube.com/watch?v=AoaaRELbhAc (robo-pitch)
http://www.youtube.com/watch?v=12fHhue80Sg (gameplay)