Several guys at my range are using them, and like them very much. the latest generation seems to have overcome some fragility problems (remember, it's slide mounted, and gets the full dose of slide recoil).
One guy has one on his Glock27 carry gun. I shot it, and was duly impressed...easy fast multiple hits on an 18x24 plate at 50 yards...in fact much faster than the iron sights on my G19.
Mickey Fowler, the former speed shooting champ, uses one on his carry gun, I'm told.
[This message has been edited by Covert Mission (edited February 09, 2000).]