We, too, use Canned Replies.
But there's still a very clear business case for good search and Peter M is exactly right - having an 'include all words' policy for returned results makes the search string feature almost unusable.
It's fine when we are searching for the name of a particular issue which is quite unique. However, try searching for a phrase with common words in it and the results are no help at all.
We have a 13GB database of customer support and the lack of good search is costing our staff a lot of time. Some of them have even started writing down ticket numbers on paper because it's so difficult to locate instances of historical issues -just like Peter is describing with a bug that needs further background information but isn't from the same customer.
You know a search system is not meeting your needs if people have to resort to pen and paper and then email each other to see if anyone else remembers the ticket that was associated with a prior-reported bug!
A simple solution would be to allow the use of quotes, as search engines do, so that "abc xyz" (entered with quotes) is a restrictive query looking for those two words occurring together in that order, whereas a search for abc xyz functions as the current system does.