This has been driving me nuts as well... I've got two SP2's, and they both have the "maintenance in progress" going all the time at random. I leave it running idle intentionally for this reason, and nothing helps.
My question, what the heck is it actually doing or think it's doing? I've got three other Windows 8 laptops (now upgraded to 8.1) and I've never seen this icon or message on any of them.
I've let it run for hours, I've restarted or powered down, only to have it constantly come back.... if it's legitimately achieving something, I'd like to know. I've googled and nothing really comes back. I have to think this is a Surface Pro 2 problem. I'd love someone to tell me what it's doing all the time if nothing else ha