Nothing, let me stress nothing upsets me more than being thanked for my patience and understanding. The nerve of assuming you are entitled to either metro speaks fucking volumes about your service.
How about those 'we appreciate your patience, your call is so important to us' on hold messages when you try and call a bank, telco, [insert govt dept], etc and you're only another 35 minutes from the next available agent? Because those make me wanna rip cute stuffed toys apart.