Well, I was rather hooked by the P90, which I was able to test at work.
It has some flaws for sure (Sights), but still, it's a very impressive weapon.
Back in these days, I shot both, the P90 and other Submachine Guns in full-auto, and the P90 was the one with lowest, if any, muzzleclimb, even one handed. Now combine that with the outstanding ballistics the ammo has, and you have good weapon, if issued to the right hands.
It's only sad, that they are not that available in Europe, like they are in the US.