i can basically knock out anything i want to do to a bike faster than a shop can take a look at it now. including derailleur adjustment and drivetrain setup. so uh... yeah. it's worth it.
minus wheel assembly. which is next on my list of things to learn.
but don't fool yourself: there's doing something 'well enough' and there's doing things 'right.' you want to do things right. always.
also, tools are great but supplies are paramount. you need gloves, rags, workspace, and gojo more than you need a headset press. ****, with the amount of time i spend wrenching it's a cardinal sin for me to not have a workstand.
everyone who's interested in this ethic of work idea or the joy behind "being a master of one's own stuff" on a philosophical level should read
http://www.amazon.com/Shop-Class-Sou...mm_pap_title_0 matthew crawford's nyt bestseller.