So I just upgraded a large forum from 1.3.5 to 1.4.1. Immediately after, the forum is running slow... Is there some kind of upgrade process that is running in the background that is making this thing slow? Or should I be worried?
If they have numbers like that (which would generally be logged in slow queries or via EXPLAIN), they should be able to give more specific details of what those queries are and thus would allow us to comment.
But if you haven't made the index change referenced above and you're seeing performance issues, you really should.