I've been using the smart carry for over a year now. I must say I had doubts about the holster before I bought one. However, here at school it seemed the best option for deepest concealment since ankle carry does not work for me.
First of all, if you follow instructions, aka wear it on your hips and not your waist it will be very comfortable. A lot of the people who I've seen try it on and not like it wear it on the waist. This causes troubles when you sit as most with bellies end up pushing up against it. Around the hips most find it much more cofortable.
Pros:
*Its truly deep concealment. Yes, I even wore it under board shorts on the beach once.
*Even the experts have a hard time spotting that you are carrying
*It can be really comfortable
*There is a second pocket for an extra mag
*The gun remains very secure, brings a new meaning to retention?!?!
Cons:
*Unless you have elastic pants, the gun will be a challenge to get out while sitting. You have to do an acorbat dance to have a fast draw. But thats a trade-off I'm alright with for such deep cover. Two tricks to fixing this is to first buy pants one size up. I also buy the ones with elastic built into the fold. It gives you just enough expansion as you dig for the gun to pull it fast while sitting!!!
*The holster is specific to body type as to what you can carry as per size of the gun. I personally can't get a 1911 to fit down there but I'm short.
Now standing up the draw is very quick with practice. Go to utube and type in sparrow assassin and you will see similar draw techniques. Its also the last place most look. I've had friends pat me down and miss it completely. Most who hear I carry in this manner say they would never because well they are worried about kaboom on something that needs no kaboom. However, as stated above, this is not an issue for MOST of us out there. If you have the holster on your hips the gun sits straight down. Also the holster can be offset to the right a bit so that the handle buldge blends in with a wallet or something in the front pocket. This also takes aim off well, aka see above posts.

I'm sort of fanatic about the holster for its deep concealment, but when I go into the big cities, I still carry IWB at 4 o'clock.