I was trying some fixed query searches today in order to find all documents recently updated across the MOSS farm. So I set up a Core Search Results web part to find all documents throughout all site collections, and view by modified date and return, say, the 10 most recently modified documents.
I got a bit of a shock when I switched between ‘search by relevance’ and ‘search by modified date’ preferences in the query. By Relevance the search took a reasonable ~0.3sec, however by Modified date took a somewhat more sluggish ~7secs, that quite a difference in my books! Not sure why, but I’ll avoid that one in future!