To the OP
Three months ago, after looking at the Walther, Ruger, S&W, and SIG, I went with the Mosquito.
I am a brand new shooter, no handgun experience, and my intention was to learn and practice with a .22 before buying a more typical defensive caliber. This may or may not have been smart, but it is what I did.
The Walther and Ruger were just small enough in my hands that I felt clumsy handling them. I liked the feel of both the M&P and the Mosquito. The M&P only operates as a single action. Since I have not decided on the next pistol and I did not want to limit my practice options, I went with the Mosquito. (Well aware of its spotty reputation. But my review of multiple shooting forums, and Youtube, revealed complaints and issues with all four. Caveat Emptor.)
1200 rounds so far, no failures of any sort. I understand 1200 rounds is not a lot of shooting, but the results are what they are. All ammunition to date has been CCI Mini-mags using both the 36 grain HP and the 40 grain RN. I am just about to start experimenting with other ammunition.
I am using the spring that was in it when I bought it. I cleaned it thoroughly and lubed it, using grease, per SIG instructions before shooting it. I also disassembled, cleaned and lubed the magazines, which had a tacky feel right out of their packages. My average session is about 200 rounds and everything gets cleaned and lubed after each session.
As someone learning to shoot, I won't talk about grouping, but I consistently hit in an 8 in square target at 15 yards. An instructor shot it after one of my sessions and did much, much better than that, but I didn't keep the target, so I can't provide any measurements. It certainly seems to shoot well enough for my use.
First post here, please don't beat me up too much.