I've been using the smartcarry for a few years. Love it. I did have to alter the holster a bit so it was more comfortable. Basically, I narrowed it down to the shape of a pie wedge only rounded at the muzzle end.
I mostly carry an M&P9c in it, but when more form-fitting dress pants are required, my airweight j-frame fits in the same holster and really disapears.
I'm about ready to either replace my third smartcarry or go with some other deep concealment rig like the threespeed.
I almost bought the treespeed because I really like the extra bit of material which extends above the gun. While this makes it easier to get a fast grip on the pistol, it makes it hard to conceal in the manor I use the holster most.
With the smartcarry, I'm able to tuck my shirt in behind the holster and gun and let the pants hide the gun. The threespeed holster's extra material doesn't lend well to tucking the shirt in, but it would be great for those who go untucked.
I personally like having the ability to put my ccw permit in there as well. It's a deep concealment holster, so no one is going to see the gun or acccidentally touch it. Therefore, no LEO is going to be asking for my permit unless I've already drawn the extreme emergency tool to preserve a life. As such... no LEO will be thinking I'm going for my gun when I'm retrieving my permit because the LEO will likely already have my gun... We don't have to tell the LEO about the gun during traffic stops in this state.
I also wish the threespeed would be offered in white because that's the color of my underwear.
I've just about decided that I'm gonna go with the .Five-O holster...
http://jjracaza.com/videos/five-o-concealment-holster-commercial/
I'm just not sure it is going to be as comfortable as the softer materials used with the smartcarry and threespeeed. I also wish it was offered in white.
There are a lot of guys out there who really frown on these holsters because of the percieved slow draw times, but as the above video shows... it's quite fast.