Re: anyone use the 5.7 pistol?
Put simply, the 5.7x28 is a shitty cartridge for shooting at things that are alive that you wish to be dead. Unless they're really small, furry, and reasonably close, I suppose. The entire raison d'etre of the caliber is to provide close-range penetration of soft body armor in a handgun-sized package, no more. In absolutely any situation other than defending against body armor-wearing assailants, you'd be wildly better off with virtually any other typical sidearm on the market.
As for the pistol itself...from a handgunner's point of view, it's a rather lackluster weapon. The trigger isn't all that amazing for a single action only weapon, the slide release is a pain to use, and it has a certain cheap plastic feel that you just don't get from most polymer-framed handguns, even Tauruses. The old rental 5.7 seemed to always be out for service due to various magazine issues, and finally gave up the ghost after a relatively short lifespan of use. Call it 2.5 stars out of 5, being generous. If I had a bunch of money lying around stinking up the place, and someone offered me a 5.7 for less than $500, I'd give it at least a moment's thought. Anything less and it doesn't even register.