Originally Posted by WhyFi

With hydraulic systems, the gap between the pads and rotors self-adjusts and isn't user adjustable. There's no toe-in or anything like that when you replace pads - you simply push in the pistons, remove the old pads, put in the new pads and give the lever a few squeezes to re-position the new pads once the wheel is back in. It takes a screwdriver and so little time that it's not worth cracking open a bike maintenance beer.

Free stroke (lever travel before engagement) can be adjusted on some levers (generally Ultegra level and above).