I only have to maintain a relatively small environment, so I don't have the same kind of personal experience as someone in a large enterprise. However, I have talked to a number of colleagues that claim that it doesn't need a lot of support, if it's implemented correctly.
In fact, I have a friend that is responsible for this at a Fortune 500 company who told me that support for drive encryption in their environment is so basic that it's most likely going to be handed over to their help desk. So, if you plan it out in advance and do it right, you can save a lot of headaches and potentially offload that task. You'll still have a little bit of maintenance with patching, but basically it can be hands off, if its done the right way.
Check out the entire Storage Encryption FAQ guide.