I've got a Mosquito, and as much as I liked shooting it, I can no longer recommend buying one. After several thousand rounds, the extractor on mine cracked, and is no longer ejecting reliably. Flaw in the metal, who knows. Not a common issue with the Mosquito, not a design flaw, just bad luck. Not a reason to not buy one.
What I do consider a reason to not buy one is that Sig doesn't have spare parts. Recoil springs and magazines - that's it. They want me to send it back - for an extractor. I'm sure their service department will take care of it, but I know I'm going to spend a lot more in shipping than ordering an extractor would have cost. If I'm going to keep a pistol for the long haul, I really want the ability to buy spares so I don't have to ship it back for little stuff.
So, Ruger Mk I/II/II, ( I have a MkII that's been great), S&W 22A should be a bit cheaper, Walther P22 was a nice shooter and way too small for my hands, or the S&W 17/617 revolvers.
I would like to try the SR22 and the M&P 22 pistols. One of those would replace the skeeter nicely.