Though they are marketed as a concealment holster, I agree that unless they are under heavy clothing, they don't conceal very well. For open carry or a range holster, their function is excellent.
I have Serpas for an XD-40 and an HK-40 USP Compact, and the fit is perfect, though as I said, the concealability is poor. Where I have really found good utility is for a Taurus Judge that I use as a snake gun, wearing it in the boat or on a tractor. With its excellent Level 2 retention I have no worries that the Judge will end up in the lake or under the bushhog, and it easily cleans up after an afternoon of sweat and dust after mowing.
XD-40 service, XD-9sc, member GeorgiaCarry.Org, National Rifle Association, Gun Owners of America, North American Hunting Club, Rocky Mountain Elk Foundation