I got my WE M4 yesterday, and have done some garage goofing arounnd with it. So far, everything is excellent. I carried out some of the preventitive maintenence listed in the Wiki above (removed and loc-tite'd the #36 screw, and I'll shortly get around to polishing the cylinder that the #122 o-ring slides into), and it's worked flawlessly through about 10 mags. I can't test accuracy very well with only 20 odd feet of shooting distance, but my club is playing tomorrow, so I'll do some longer range testing and chrono it.
I won't actually be able to game it, since I've only got the one mag, sadly
. I'm badly torn between ordering 6-8 current mags ($38 each + shipping is pretty reasonable), or to wait for either the 50 round PGC mags, or the WE Co2 mags. If only WE would make the Co2 mags with a slightly higher capacity then 30...