Harry, no feed problems, but I have not had a serious go yet. I've only fired a couple of mags through to test the conversion. I got no garden, no yard, and the missus gets irate when I fire BBs across the flat.
The M9 mags don't click in quite as positively, I did notice. They are secure once in, but you got to push them in solidly. If you are a bit limp-wristed with them, they come straight back out. Shouldn't be a problem in the long run.
I will do a proper write-up once I can get them somewhere to really put them through their paces, I swear it.