I use a SmartCarry pretty much daily and have for a number of years now. They work great, and especially in a NPE. No need for any kind of cover garment or anything special for that matter, just your normal attire, and you dont even need a shirt. I have a number of them, and find they are one of the most versatile holsters I have/use, and wont be without at least one.
They may not be a quick draw holster, but they are not at all slow (on the draw) once you get used to them. They are the quickest and most comfortable of any of the other deep concealment type holsters Ive used. Even when seated, they are readily accessed, something pocket carry doesnt usually offer.
I picked up a Thunderwear version off EBay last year to try out, and I wasnt impressed at all. Im not sure if it was a knock off or not, but it was marked with the Thunderwear logo. I did email Thunderwear inquiring about it (twice), and never received a reply, so Im assuming it is one of thiers. The one I received was not in the same quality league as the SmartCarry's, and I was easily able to trip the trigger of one of my Glocks through the fabric, something I have not been able to do with the SmartCarry's I have (I normally carry a 26 in mine).
I would definitely recommend the SmartCarrys if you havent tried one. Like anything new, they do take some getting used to, but I think once you do, you wont want to be without one.