They're okay. Some folks really like them, and the quality has been a bit of a mixed bag.
I have the GSG and like having a 1911 framed 22lr. I don't like that there are several really low quality parts in these guns. I'm aware of four of them at my local range. Three (including mine) have fallen apart before reaching 1000rds. Two were broken guide rods, one a barrel bushing...all literally broke in half. I know the guide rods were due to lousy quality. I suspect the bushing can be attributed to the end of the threaded barrel coming loose.
If you get one, invest $25 into an upgraded guide rod. Mine functions okay now (not great) with it's fair share of stove-pipes. I really think the S&W MP22 is a better gun for similar money...but might be a totally different style than you're after.