652217745115 helps with recoil (must modify for Gen 3), though I've not found the it to be harsh in the least, both on Gen2 and Gen3 9mm. With the 5.7, you can hardly call it a kick. All three o’ mine have a Strike Industries brake: King, Mini-King, Checkmate, respectively, but honestly you don’t need it – just looks kewl. Gen 3 is generally a vast step in the right direction - the trigger is bit longer and wider, aluminum w/ serrations - it's not backwards compatible to Gen 2, but you can Dremel it into submission. The trigger feel in Gen 3 is miles ahead of an unmodified Gen 2, but in both 9mm and 5.7 the trigger bar leaves much to be desired. mCarbo can help with 9mm, but there's no option for the 5.7 which has a longer trigger bar (by about an inch), thus even more susceptible to warping during high stress (like 150 rapid rounds in 105 degree dry weather). Once the trigger bar bows, it no longer makes full contact with the sear - the behavior of the trigger then is akin to safety being on. This btw, can be sometimes reproduced with unmodified Gen 2 9mm, but mCarbo’s bar fixes all that. No such fix with 5.7, which, sidenote, almost completely lacks a reset trigger click. The 5.7 also has a different trigger spring arrangement - there's no tab on the bar, but I got the mCarbo flat Gen 3 trigger, which works just fine in the 5.7. mCarbo’s SS hammer bushing works on both Gen 3 9mm and 5.7, but only 9mm takes the SS ramp – 5.7 doesn’t have one (doesn’t need one – works differently) Obvi, I like Gen 3 well enough ‘cause I got two, but I do miss the G17 grip on Gen 2 – 3rd gen (9mm) only comes with G19 length, but now you can get spacers for G17 mags. No such issues with the 5.7 as it has a full size grip (much like FiveSeven's) which is very nice.
Gen 3 is a KISS gun – no complications. Not your tried and true AR, but absolutely a blast for occasional fun. Makes an OK truck gun, but I wouldn’t take it into a full blown scenario. The 9mm can be finicky in that when new, it requires a bit peppier rounds like Winchester Red, else you get the occasional stovepipe, but, as it settles after few hundred rounds, you can run the CCI soft stuff 115gn. 5.7 eats everything and anything – sure, since the 5.7 offerings are slim compared to 9mm. Far as the lack of sights – the Gen2 ones were useless since you had to smush your face into the bolt tube to get a proper sight picture, so in a way I’m glad they didn’t bother with the ridic front sight – MidTen red dot for less than $30 and AR style backup sights for about the same will get you going just fine. Go Romeo if you feel a bit snobbish, but for the most of it, just KISS…