[Mediterraneo10]

There are some really crappy low-end mechanical disc brakes around, but the TRP Spyke and Avid BB7 are solid and commonly found on touring bikes. If you plan to cycle 30,000 km through lots of remote terrain (e.g. Alaska–Ushuaia or Europe to Cape Town via West Africa), then they are as trivial to maintain as rim brakes, without however destroying your rim.

I have cycled down some of the world's great mountain ranges, and I have never had complaints about my Spyke's stopping power.

[veggieburglar]

Agreed on Spykes and BB7. Mech discs are essential for long touring... who wants to carry a bleed kit? In all other cases though, I will prefer the modulation and stopping power of hydraulics, both on the road and on the trail.