We have a blog with:
and our tag pages are very slow after upgrading to 3.1.1.
On smaller blogs and on tag pages with only a few postings it does not seem to be a problem. But we have some tags with 400-500 posts and that tag pages produce slow queries now.
We have isolated the problem a little bit. It is caused by the changes in "/wp-includes/query.php".
If we use the old query.php (3.1) it is lightning fast. If we switch to the new one (3.1.1) it takes 10-20 secs.
With regards from Germany,