Exactly. You should stick with the almighty 45. Big holes are awesome. If you want to shoot something that is nasty fast check out 9x25 Dillon. I have been dreaming about getting a glock 20 just to do a conversion.I have one and really enjoy shooting it. Very light recoil, very accurate and nice 20 round standard mag capacity.
Biggest problem is the ammo is really hard to find lately. For about the last year finding 5.7x28 anywhere has been like winning the lottery. It has popped up recently but not in any quantities like standard caliber ammo. This is a shame because it really is a nice pistol to shoot.
As for people complaining about it being an ineffective round, you will find people who complain about any pistol caliber if it isn't the almighty .45ACP.
I hate to say it but I find 5.7 all day long at Gander for way cheaper than any LGS. Infact, Gander had it on Black Friday for about $2 more than I was paying two years ago. American Eagle 5.7 is about $25/50 and FN is $31/50
I have not fired the pistol, but I love AR in 5.7. It is super fun to shoot, and everyone that fires it, loves it.