For comparison of different systems, I am putting up a pic of my Burton heel (same step in, other engaging system). I only know of myself and Rob (he has been using this for years) using these. I have no problem with them, but when you wanna borrow/lend boards with fellow carvers, you have serious incompatibility problem. The metal rings on these heels seem pretty sturdy and big. I do check them on regular basis, but as others already pointed out (about intec heels), checking does not guarantee a safe ending. I think this may be a serious issue and I wonder whether other/better heels are being considered (Fin?).
P.S. I realize constructing and molding a part like this on manufacturing level can be pretty costly.