I TRY to do it all... simply because I love bikes...I won't quit my day job any time soon, but if I didn't work on bikes, I don't think I could make it through my day job... I'll never take the place of a good, competent LBS mechanic... but I still love to do my own repairs as much as possible... Welding, painting and fork maintenance I generally leave to the pros (although I have rebuilt a fork, and do plan to begin dabbling in welding and painting this year...). The key thing is show no fear... anything is possible to master...
Build-ups... I love creating/building bikes, mostly steel hardtails and classic retro-bikes. Between Nov 2007 and Dec 2008 I built approximately 8 bikes.
Wheel-building - This past year I got more into wheel-building, by doing a few buildups for myself, and for my friends (in return for a "no complaints, dude, it was free" policy). When the dust settled, I realized I had built 3 sets of 29er wheels, 3 sets of 26 inch wheels and 3 sets of 650B wheels, along with half a dozen individual wheels... WOW, it's not that difficult... If I CAN DO IT, SO CAN YOU!!!
Hydraulic brakes - I don't understand the hesitation... I've built at least half a dozen sets of hydraulic brakes, including cutting hoses, connecting calipers and levers, bleeding, etc... It's really not difficult, and I personally think it's fun.
Tubeless Tires - I've converted several sets of wheels to tubeless... I'm starting to become an expert in the use of soap, water and air to getting stubborn tires to properly seat on the rims...
Franken-bike - Ah, a category of bike mechanics unto itself... Where you combine or modify components that really have no business being tweaked or used like this... For example, I reconfigured (that is, opened up and F'ed with the cable setup of) an internal geared hub... kinda like taking apart a Rapid-fire shifter... As long as you keep a cool head, there's no reason you can't explore.... I also recently put 5-6 speed friction shifters on my 9-speed Fargo (when others claimed it couldn't be done... bull....)
To me it's all about creating... building and riding that perfect bike.
Peace,
BB