Things I liked: it fits almost all my guns, including my Sig-Sauer and, surprisingly, my S&W Model 686, although it is a bit of a tight fit for the S&W.
Things I would have changed: Not much. Leapers already offers it in various camos, so you already have a most excellent shoulder holster. Yeah, the only thing I'd change is offer it in a left-hand version.
What others should know: For Peter, those dangly straps are meant to be put on a belt, like a tactical belt, so that the holster is actually secured. Also, be aware that the mags are appearently kept upside down by default, so flip the holders before using(unless you like them that way).
Things I liked: This is basically the only replica of a concealed carry weapon you can find as an airsoft gun, so that's a definite plus. Its size makes it really quite easy to holster as a backup gun, as its firearm counterpart is as well. The P99 Compact also has more than decent power for its size range, and has good accuracy to boot. It even only costs $15 plus shipping. If you want to practice drawing a concealed carry weapon but don't want a potential for putting holes in something, then this is pretty much your only alternative.
Things I would have changed: Not much. Probably a stronger spring for more power(I've opened up this airsoft gun, and fitted mine with a spring that gets 280 fps with .20g BBs).
What others should know: Just keep in mind that this is a Walther P99 Compact replica. That means that this particular airsoft gun is intended to backup a full-size sidearm, in case that sidearm fails or runs out of ammo. It also is somewhat less comfortable to use, since it has to be smaller to help conceal its presence. If you have bought an ankle holster, this is probably the best pistol to put in it.