There are three parts to my findings with the WE M&P thus far (eventually I'll do another part or two). You can find the links to my blog, Overhoppers, in the text below.
"Cheers, WE. You’ve come quite a ways from that crappy old 1911 I owned. I’m actually impressed with this M&P!"
Review (mostly externals): Overhoppers WE M&P (DE) Review
Click the above link to read more and for more pics.
Problems & updates: Overhoppers WE M&P Update
Click the above link to read more.
Fix (for full-auto): Overhoppers WE M&P Fix
Click the above link to read more and for more diagrams/pics.
[Note, this image is not mine, it is directly from WE; I've linked to it in my blog]
Long story short (and for those of you who are too lazy to click the links to my blog):
A cool gun with a mushy trigger and snappy recoil. Decent performance in the cold for a WE, smaller magazine capacity than most other Airsoft double stack 9mm mags though. Seam lines apparent in plastic, finish on outer barrel crappy. Looks good, feels good. Ambidextrous slide stop, interchangeable back straps work as advertised.
Problems with performance and shooting out of the box. Fixes generally easy, though not for the mechanically challenged. Sear may need to be filed down, hop up arm needs to be filed down - both require partial disassembly of WE M&P, beyond a simple field strip. With minor fixes for the major known issues, the WE M&P is worth the time and money (especially considering how there's no other full-size M&P GBB out there yet).