I saw one today at my buddies shop while picking up a
Marlin 336CB. It was well made, lightweight, but rather unwieldy in two respects:
One, it's grip is very long to accommodate the round, very much like a Glock 20 in 10mm. Not uncomfortable, just unwieldy.
Two, its safety is located forward on the slide above where other semi autos have a slide release. The slide release is further aft where the safety would normally be on the frame. I found that to be more than unwieldy, but downright confusing, especially in the heat of battle.
IIRC the cartridge as sold to the public is not the same round that the Praetorians use in theirs, and essentially what you have is a hi cap, expensive, .22 Mag. Personally, I would rather have two Glock 22's, or a Glock 22 and a 27, or a G22 and a Smith Airweight, for the money it costs for one of these, even at current prices.