Last fall I bought a Surly Troll with disc brakes; my previous bikes were all 80s road bikes with caliper brakes. I'm never going back to rim brakes. Discs work better overall, especially in wet/dirty conditions where rim brakes start to get sketchy. They may be a bit heavier, but maintenance isn't a real big issue (at least not with mine - Avid BB7s, which all bike tourists swear by). They're somewhat more expensive, so maybe there are high-end rim brakes that would be better than what I had been using, but discs have other advantages too - they don't wear your rims out, they work fine if your wheels are covered in mud or your rims are out of true (this may be more of an issue with off-road touring) and just overall better stopping power.

Hydraulic discs seem a lot more high-maintenance. I wouldn't really care to use them, although people talk about how amazing the performance is...the performance on my set is just fine.