I am installing a 4 wheel, 6 piston calipers, complete Wilwood disc brakes system, including going to a Wilwood master cylinder.
I'm keeping my brakes MANUAL, and this new system is not a "budget" setup by any means. I'm keeping manual brakes because I prefer actually being able to modulate my brakes, rather than them being more like an on/off switch. I also know there are ways around having low vacuum and how that's bad for power brakes, but once again, the feel of manual brakes is my preference, and that's in a 70 Roadrunner, so more weight to stop than an A body.
Short version: unless you have leg weakness, I'd say don't hesitate to do manual brakes. More room under the hood too!