Great thread.
I'd like to add a vote for cantilever brake setup misery. I must say it warms my heart to see others share my aggravation.
I'm an engine builder, and can split apart, check, clean, prep, and re-assemble a fairly complex modern 2-stroke engine in an afternoon. I've had it take just as long to set up my Avid Tri Aligns. No matter what cantis I set up I always seem to be right at the limit of pad angle and height in order to hit the rims square and not be dragging on the tire and leaving a nice old impossible to remove black line (on my UmmaGummas no less!) on my sidewalls. If I get that right, it's a sure sign the pads are toed in the wrong direction, and I have to back up and do it all over again.
Cabling isn't too bad, unless of course I'm using some NOS period correct outers, in which case the chance of cutting them too short nears 100%.
Why is it no matter how much I loosen clamp bolts, my brake levers/shifters always scratch the hell out of my bars when I take them off? I dread swapping stems for this reason.
What do I like? I like it when I've put my nose to the grindstone and taken a bare frame to a rideable bike in a single session-despite the aggravation and always-present 'why is this taking so freaking long' thoughts. I like polishing stuff, I like removing stuck seatposts (Victory!) and stems, and grinding out frozen-in bottom brackets-I have some expensive hand-held rotary tools for doing engine work and have saved many a frame this way.