I have 2 Serpa holsters, one for my XD45 and one for my J-Frames. The XD holster is a very good holster and I use it as my primary holster as the draw is very smooth. However the J-frame holster is not so good, and it just doenst seem to fit either of my J-Frames very well at all. Oh well. My only complaint with the XD holster is that when used in conjunction with the shoulder rig available from Blackhawk, the gun can and will fall out if pressure from the side of your arm releases the retention button. Happened to me while I was camping once, I leaned forward to pick somehting up off the ground and all of a sudden my gun is bouncing around in the dirt. Kinda scary IMO.
This wouldnt ever be a problem with the holster on a belt (unless you were upside down) but it is something to be aware of.
-c/Kord!