I said 20% of our IE traffic is IE6 which is 20% of 70% which is more like 14% so that would be a pretty large deviation from 26% when I'm trying to determine where to put resources. When you factor in trending over the next 6 months you have to realize that number is going to drop probably another 5-10% of overall traffic.
Depends on how focused you are on corporate users and the undsutry. In some industries 30% of ALL traffic is IE6. That's trending down, but slowly. Perhaps 1 or 2 points a month.
Also, 40% of 2/3 is about 26% of the whole, which I wouldn't call "wildly off base" even for your site.