I had a Pug and a smaller 22lr. They're fun range toys, but I couldn't see myself carrying an NAA for serious use, so I sold both of them. I'm not saying that there isn't a niche somewhere for someone, but for me - personally - I'd classify them as a novelty.
That novelty classification actually has less to do with the efficiency of 22mag/22lr from a sub 2" barrel in self defense applications than the size of the weapon itself, which would make access and use problematic under duress, in an entanglement, compromised position, etc.
Then there's the need to cock the hammer prior to each shot, and if it's time to not have the hammer cocked anymore because the problem is mostly resolved and the gun is still loaded, well...I can envision that as a potential problem too (in the form of an accidental bang).
As an anecdote, several years ago I was first on scene to a homicide involving one of these little revolvers. I witnessed the effect first hand - as I had before - that a single well placed 22lr can have (victim was DOA and response time was single digit minutes). I say that just to emphasize that I know better than to scoff at 22, but we all know it's generally not optimal for self defense.
I know they're small, but if you're truly in a NPE or other requisite scenario and needed/wanted something small like that, I think an LCP or S&W Bodyguard .380 could go just about anywhere an NAA could go, except with a little higher probability of survival. Even those little .380 pocket pistols can be hard to grab onto and fish out of a pocket under stress/pressure though, which is why I've almost exclusively gone back to J frames for lazy, er, pocket carry-the grip on a J frame is just more realistic.
I've played with a lot of this stuff under pressure on mats (outside of other formal classes, ECQC, etc), and the conclusion I've arrived at is that I think a fixed blade is the answer for most problems people envision when they mistakenly think a micro handgun is the solution.
So, in summary, I think the NAA stuff is cool, but I personally wouldn't feel comfortable with having to rely on one of them to keep me upright.