When viewing the issue tracker of one of my projects, I am often interested in seeing the highest priority issues. To do this, I go to the issue tracker and click on the exclamation mark (!) at the top of the third column. This sorts by priority with the lowest priority first and I have to click again to get highest priority first.
I can't imagine that many users are interested in seeing their lowest priority bugs first when sorting by priority. I believe it would be more intuitive for the first priority ordering offered to be highest-priority first. If users really want to see the lowest priority at the top of the list they can click again to swap the sort order.