I just bought a NAA mini-revolver today in .22 magnum. Also got a pocket holster to go with it. I carried it out tonight in addition to my SA XD-9 Subcompact IWB and I almost forgot it was there. After I bought the mini-mag I drove directly to the range and put 500 rounds through it. I got the convertible model that also included the .22lr cylinder, so putting lots of lead down the range was uber-cheap.
I was pleased with the accuracy...I was able to get 2-3" groups at 10 yards once I figured out how to hold and aim the little bastard. I was also pleased with the reliability. Out of 500 rounds I had one Federal "golden bullet" .22lr dud, and that wasn't the gun's fault. All of the .22 mags I shot were spot on accurate.
I was choosing between the mini-mag and the Kel-Tec .380. I shot the KT the other day (a friend's primary carry gun) and had two failures in one magazine. Not acceptable. I would rather have a smaller bullet that I can consistently put between the eyes than a larger one that may f--- up after one shot.
Besides, my primary carry is the XD; I've yet to have a failure after 1,000 rounds, so I'm pretty sure I won't need the BUG.