I personally would say fixed gears wouldn't be that good for touring, mostly because your legs NEVER get a break. If you're moving, so are they. No coasting.
That's not to say it can't be done, but if you're going 80+ miles a day, next to someone even on a single speed that can coast down those hills, or just give their legs a rest, it's pretty easy to see that you're going to be more tired than you would had you had a freewheel. A single speed really requires no more maintenance than a fixed, so I'd suggest that as a minimum, but most people that tour have a few gears. There's just such varied terrain, and you're usually packing a fair amount of crap.
I ride a fixed gear everyday, and I love it. It's a tiny little track frame and the responsiveness can't be beat, especially in downtown traffic, which is where I am usually. There are lots of pro's to them, but I'd say touring is not their best suit.