I am currently in the process of completing an Exchange 2003 to Exchange 2010 mailbox migration. The default public folder database for all of the 2010 mailbox databases is the exchange 2003 public folder database.
After a user is migrated to the Exchange 2010, when they try to search public folders using the instant search on outlook 2007 or outlook 2010 clients, the search only highlights the term in the results but does not filter out the mail that does not fit query. You have to scroll down through all of the mail to see the highlighted results.
I know that this sounds like an indexing issues, but i have tried everything i could to repair the indexing and completely rebuilding it.
This does not occur for all users migrated but a bunch of them.