Couple things I didn't care for, and of course just my 2 cents. I don't dig appendix, not because it doesn't work for some but it really doesn't seem to work for me. But I do appreciate that it's quick etc, but I'm not sure it's quick enough to justify the comfort or lack of comfort in my case. Particularly when seated, either in the car or around the shop, appendix just puts the gun in my way when sitting. Where typical hip carry it's out of my way and comfortable for just about anything I do whether it's sitting in the shop, driving or climbing under the car to fix something;)
Also on the video my biggest complaint, I really don't like that thumb method to clear the shirt. Seems far too likely to fail and by my eye did fail a few times on his fast draw examples where he was muscling the gun draw through the shirt impeding the draw. Much better using the fingers but I think teaching the thumb move is a bad idea. I'd rather see him teach something that works all the time even if it's a hair slower, consistency I think is important on the draw. Also the reason I'd say to keep with something that keeps the gun mostly in the same basic position on the body, your draw motion will basically be the same.
It is what it is though, everyone has their own opinions on these things. But my own is that I really think appendix is an option for some circumstances and some guys, but I also think over the next say 10 years, we're going to see it become even more of a niche carry method than it is right now. Firearms and holsters go in trends particularly in position of carry. And typically it always swings back towards normal hip carry over the years because it generally works for most people. Much like small of the back carry, shoulder rigs and most all other non standard carry methods that have become super popular through movies and media in the past. And those carry methods bar maybe small of the back do have merits in their niche much like appendix, but I still think for the broad strokes normal carry methods on the hip will work for more people and generally be more comfortable.
BUT, that's just my 2 cents. If you run appendix and it's the best thing ever;) I'm cool with that as well;)