The "J-hook" concept isn't new. I first recall seeing it in an old Rogers (pre-Safariland acquisition) IWB rig. Wilson is offering a holster that is very similar to the old Rogers design as well. Hoffner's uses a similar arrangement on their kydex IWB (the Hoffner's IWB is cheap and amatuerish looking, but works very well.
The advantages offered by the J-hook arrangement is easy on/off (without having to unthread one's belt), good security agaist the holster coming out with the pistol, and a thinner cross section than most other arrangements.
I have an earlier Blade-Tech IWB that I am going to send back to them to have j-hooks fitted. They expressed a willingness to do so some time back, but I've just been too busy/lazy to send it back.