I'm a fan of the little pistols- simply because they are neat, unusual and really there isn't anything out there that quite fits the category that they cover except them...or maybe a Baby Browning or something else similar.
They carry about like a pocket knife, and are easy to forget about because they are the only gun that can be used in any and all types of clothing, without "printing."
They are the most convenient CCW that money can buy.
The above statement does not suggest carrying one as a primary carry handgun, but if you can't carry anything larger simply because of any reason, carry it.
I wouldn't recommend being without one for any reason- whether carrying anything else or not. Preferably in the off-hand pocket for the simple reason that you may not be able to get to your primary.
We had a trooper here many years ago that went to a call and was grabbed on the right arm by a large German shepherd. The trooper, try as he might to force his way out or to his duty weapon, he couldn't. He reached into his off hand pocket and retrieved the little NAA .22 WMR and put two rounds into the skull of the dog which dispatched it.
They are small, yet handy. Don't discount them as something laughable. I don't see any volunteers to let me shoot at them with one.
"Mouseguns" definitely have a place in the CCW holder's proverbial vocabulary. To segregate these pieces out as ineffective, archaic and questionable is to relegate an important component of the freedom of the shooting sports out of existence.
Do not underestimate the importance that these little pieces provide.