I've had a G37 for three years now and love it. I've tested many reloads and many factory loads, and all exceed .45ACP ballistics and almost match the +P .45ACP loads. I think its a great cartridge. There are factory loads from 185gr. to 230grs. so there are equivilents to all .45ACP loads out there. Sure they are a bit harder to find, but the platform fits the hand way better than the ACP, all the ballistics are there, I frankly see no downside. All the newsaywers to this cartridge I find are the ones that have never fired a round in it.
I own not a single .45ACP and see no need with a .45GAP in my stable. Fits my hand like a glove. The G21 is too chunky, the G21SF isn't much better, the G37 is the perfect .45. I love having a trio of Glocks (G17, G22 and G37) with all the exact grip sizes and shapes. Reloading the GAP is easy and components are easy to find, plus I don't have to switch to large primers EVER! Whats not to like about this cartridge? I am a big guy, well over six feet tall and 235lbs, but I just hate the way the ergonomics of the G21 and G21SF feel in my hand. I refuse to own a 1911, I expect my firearms to work. Glock all the way for me.
Since I bought my G37, its seen more rounds than my 9mm and .40S&W combined, thats how much I've come to love it, and I was somewhat of a skeptic going into my GAP project.
G37, the perfect Glock!