I installed these on my Civic in July of 2009. I failed to note the mileage when I got them, but looking back in my gas logs I was able to find out when I got them. And I average around 21,000~22,000 per year. My first impression was they they were squishy. Very squishy compared to the GoodYear Assurance tripple treads they replaced. Of course I wanted mileage, so I put more pressure in them. I ended up running them around 40-44 psi most of the time I had them. This made them much less squishy, and they still gripped the road fairly well. As expected, the center of the tread wore out a little sooner than the edges. According to my estimate, I got close to 60,000 miles out of these. They werent quite to the wear indicators yet, but very close in the center. Overall they were fair tires, not really bad in any condition, dry, rain and snow. My fuel logs didn't indicate a significant mileage increase, but that was also around the time I slacked off on my driving. The first 2 tanks wer higher than the previous few, so there does seem to be a small increase. Pretty much as expected. Sorry for the lack of hard numbers.
At 40,000 miles, these tires on my Odyssey are showing perfectly even tread wear, while running sidewall max 51 psi the whole time. It's hard to compare tank-to-tank with everything else that goes on, but they gave a 0.5-1 mpg improvement (out of 21, so 2-4%) over the old Michelin Symmetry's.