Don't know how long this has been going on, but using 3.5 to search my blog, yields nonsensical results.
If I search for "tuna" (without quotes) using the search field in my blog, I get results not just for "tuna" but when the letters t-u-n-a appear within a word.
So rather than finding the one previous story I wrote about tuna fish, I get a list of other stories that do NOT have the word "tuna" in them. What the search finds are the letter t-u-n-a even when embedded in the middle of a word. So any post with the word, for example, "unforTUNAtedly" comes up, because it contains "TUNA" in it. Even searching with a space before and after the word tuna in the search field yields the same "unfortunate" results.
PLEASE fix this problem in a future WordPress revision.