I subscribed to the Talkbass thread on this pedal - the players on that thread really know what they're talking about! This particular thread was started back on 2-10-2008, and has been going strong since then... 31 pages worth!
http://www.talkbass.com/forum/f36/boss-gt-10b-404638/
For $500.00, I feel it's worth it, but for $500.00, I feel like I should be using it!