I doubt that I was the only one to use it. But probably most people are like me... they had simply stopped clicking the formerly useless "Search this Thread" button. That's why I didn't know about the new functionality until you told me . . .
There does seem to be an issue with the search results returned on a search by username, with keywords, and "older than 1 year". It seems to return a few recent posts as well, near the top of the returned items. I'll look at it a bit more next week.. I'm going out of town in the morning and won't be taking my notebook.