The P90 is indeed well designed. But since the promo is trying to sell the gun they don't mention it's flaws. And the design falls into the same trap that the M-16 did, It's tolerances are tight enough to lose reliability. And the P90 goes one further, The rounds going from the magazine into the chamber are rotated, this doesn't help the feed reliability one bit. The P90 simply jams alot. Also the 5.7mm round does have wonderfully low recoil and can defeat body armor. The downside is that it's incredibly weak, weaker then the 9mm Para round, on top of the the rifle shape of the projectile also limits it's stopping power. While it will defeat armor, most people don't wear armor anyway and a round like this will simply just go clean through you. the 5.7mm isn't a rifle around, it's supposed to be a pistol round yet it's basically acts like a baby rifle round. What good is a round when you need half the magazine to neutralize your target.
Well, That's just me, I'm probably wrong on this anyways. It's just simple logic to me.