Auto hold does not cause any brake wear. It simply locks the rear pads in place. Think about it this way. If you put your parking brake on and come back 3 years later would there be any brake pad wear? Auto H is a great system and we also use it frequently, but I can tell you it's not causing any premature brake pad wear.
And concerning Brake energy regen, this also has no bearing on brake pad wear what so ever. Brakes ARE NOT engaged when coasting. The drag you feel when coasting is attributed to the regen system which couples the alternator to the motor. Brake Energy Regen is really a bad name as the system works when coasting and has absolutely no relationship with the brakes. It only engages when you are off the gas and coasting, but again, the brakes aren't 'dragging'.
Here's another post on the same topic:
http://x3.xbimmers.com/forums/showpo...5&postcount=13