The GP100 is a great price/performance leader and beats the 686 cold in terms of what you get for the money. And with some tuning (which isn't hard to do yourself) and improved sights the GP100 can become something really special:
http://gunner777.wordpress.com/2008/08/24/ruger-gp100sp101book-of-knowledge/
Biggest limiting factor on accuracy is the sights: the normal Ruger adjustable rear sight isn't really stable enough. Bowen has that solved if you want something convensional, or go custom/radical as you want
. Or Ruger's "Match Champion" has gone to a fixed sight, another good solution.
Best DA trigger I have ever handled on any handgun was a GP100 range rental that had just had the snot shot out of it - per the range it had to have been well over 50,000 rounds. It was rock solid, dead nuts accurate and the trigger was smooth like buttah.
The place where the GP100 really dominates any competitor is in the ease of take-down. You can strip it completely apart with minimal tools and without violating any factory warrantee - Ruger even publishes a video on how to pull it apart and put it back together again on their own website and has good similar instructions in the paper manual that comes with it or the free PDF download. That gives you three things:
1) You can do your own repairs.
2) You can do your own upgrades.
3) You can completely strip it in the field if it gets something horrible in it like mud or saltwater. This feature alone makes it a fabulous backpacker's gun or other hard-use field gun.
Now, that said, Ruger has a competitor for it now: the new 4.2" barrel adjustable sight variant of the SP101. Holds one less shot, conceals easier, otherwise just as tough and modifiable as a GP100 and might be the best backpacker's gun ever made.