I don't own a GAP. But I'm an armorer and I have shot them and have talked to a lot of people that own them. I don't see that they are anything special when the ACP is available. I can conceal the 30 just fine so that's not an issue. And the 36 is even easier to hide.

There are agencies that have approved them for duty use. But again, the ballistics are just not that much different for it to be of any real advantage. The shorter frame is nice for smaller hands, but the new SF's have made that a non-issue too.

Modern ammunition components have made the differences in caliber a non-issue in most cases.

YMMV