Actually, it works quite well. I can still get a good draw on the pistol, and when I draw, it moves the entire holster up my pocket until it snags on the top of the pocket. At this point where the holster stays, and the gun comes out of the pocket, the top of the spare mag is actually sticking out of my pocket, and with the way I have it facing, it makes it easy to cross-draw grab the spare mag and insert it properly. I really love the whole setup.IMO having the mag right in front of the grip makes no sense... blocks access to the grip on the draw. Also, you'll have to swap hands if you ever need a reload (not that you will, but that's the point of carrying a spare mag, right)?
I can carry a full sized Government 45ACP it my jeans pocket. (It's pretty obvious I'm carrying, though.) I think it basically depends on the size of the pocket.
I am able to front-pocket carry my PF9 in some of my jeans but it depends on the pockets. Some fit but some are too tight/shallow.