[gtc]

I have already established myself here as a retro-grouch, so I am going to say no, they're not worth it, especially when you factor in the cost to maintain and repair them.
For example:
I just replaced my old Magura Louise discs with some newer Avid Juicy Ultimates. I needed a new hose ($40) and a bleed kit ($50) for the avids. New pads are $20+. If I ever tweak a rotor? $40. And bleeding Avids is a major PITA by the way... i can bleed my porsche brakes faster and with better results than these things.

Compare that with V-brakes which use $6 pads, $5 cables, and are serviceable on the trail with an allen wrench in case you do something stupid like tweak your rim.

And the noise argument is bunk also.... my vees only squeal after a water crossing, and how often does that really happen? There are plenty of noisy discs out there.

That said, my favorite brakes are still my old Magura Hydraulic rim brakes. Easy to bleed (though they barely ever need it), no squeal, awesome power and modulation. But kind of heavy. Kind of like my '84 Targa, I suppose.