Extractor issues persist, which show up in the form of weak and unpredictable ejection.
They're fixable and I would take a gen 4 glock over an m&p.
Or the OP could just find one of the many pre-2010 Gen 3's around and bask in it's boring reliability.
Hell, I'd buy a Gen 2 before I'd buy a Gen 4. I'm just not interested in sorting out problems that should have been fixed two years ago.
For anyone wondering the date of manufacture of a particular Glock, look here:
ht tp://glocktalk.com/forums/showthread.php?t=1287557




























