Admittedly, MNR is a good achievement for the PSP, but it is seriously hampered by some dodgy control schemes of which you are limited to two types. The default system is a complete waste of time, and the second layout makes the game just about playable.
The game itself is nice to play online, but as is typical of most PSP multiplayer games, in the UK don't expect to find too many on it, and in a few months it will no doubt be an almost dead community. The single player is ok, but it does feel a bit childish with the acting and cut scenes. Overall, a decent game compared to it's alternative on a different format (Mario kart), I just wish they had made the control system a little more adjustable.