Did you see the picture of the trials tire on one guy's bike after the Walden trip? I think it was posted on ADV. He wasn't just missing a few lugs - it was like the tire was scalped. I'm not convinced...
The Maxxis desert tire is appealing to me as well - I might try one of those next in the rear.
The Scorpions are popular, but obviously there are dozens of different models so it's important to state of you have one of the MX's or the new XC's that are DOT legal. I mounted the XC mid-hard on both front and rear a couple months ago (good reviews, stiff sidewalls, plus the DOT legal aspect since I'm on the pavement some), and I'm pretty happy with the rear tire for what we've ridden. But after 500 miles on the rear tire, the center lugs are showing wear. No chance it'll last as long as a 606, but I'm hoping for better life than the softer MX options.
I don't like the Scorpion XC front I have - seems squirrelly (hops around a bit) on higher speed sections. I might try something different up there. When I was doing some internet research, there were good reviews on the Dunlop 755 and 756.
Good thread choice.