I am probably one of the few members here that actually has a pistol in .45GAP (G37). Ammo is not as plentiful as the .45ACP, but I am reloader, so it really isn't an issue for me. Once I aquired enough brass to keep me going its been smooth sailing! I go through about 4K of .45GAP rounds per year and from my experience its been a great round to work with from a reloaders perspective. Its very straight forward and there is a wealth of info out there, but the Lyman's 3rd Edition is one of the best for loads, including the 230gr. loads that I prefer. Because you are using regular .45 bullets you have a huge selection to choose from, its really a reloaders dream, plus there are many powders to choose from. There are several stores across the country that regularly stock GAP ammo, places like P&D and Ellwood Epps are places that pop into my mind. Ammo can be pricey, but I've picked up boxes of WWB at gunshows at reasonable rates, sometimes even less than ACP, although with the GAP the availability is the issue, it just isn't as plentiful.
Feeding issues have been non-existant for me, I don't recall ever having a problem with extraction, feeding, firing etc. I use a light taper crimp on all my reloads and don't tolerate garbage reloads. Alot of the published Titegroup reloaded data at the lower end barely cycles the gun and spits empties a foot away...the G37 keep chuggin' along. I've tried 185gr. Hydra-Shoks at 1090fps and WWB 230gr. JHP's at 850fps and everything in between. Reliability has been 100%.
Don't let all the neysayers talk you out of this cartridge if you are serious about it, there are alot of critics of it, chances are they have never shot one or will admit that. For me and everyone that has shot my G37, the resounding response has been positive. I chose the GAP round because the G37 frame is the same size as all my other GLocks, not because I couldn't handle the size of a G21, I am well over six feet tall and have big mitts. The GAP round is just well though out in my opinion, I have had no second thoughts with mine for the three years I have had it. In the last couple of years I have probably put more rounds downrange it it than in all my other glocks combined....that's how much I like it! Take the leap, you won't be dissapointed.
Both the .45GAP and .45ACP have their positives and negatives, from my experiences I would do it again, I have enjoyed being one of the Canadian .45GAP pioneers!
I think tomorrow I'll pull the trigger so to speak and get 'er done. I was looking for something a bit different from the mainstream and I this is going to do just nicely. 
