The Best I have seen about this, is the Four Seasons in Vegas. I had a 4pm checkout through Amex FHR, had the DND sign up, and, the maid saw me walking in the hallway, and asked (about 12pm) if I wanted her to make up the room before I left so it would be fresh. Other than that, that is the only time I ever heard from her.

The worst was the Hyatt Key West (the one by the airport). I had the DND sign up, and was sleeping in due to a late night. I had the deadbolt and the chain on, and at 8am the maid just kept knocking and knocking, and at one point actually overrided the deadbolt (I didn't know this was possible). I called the front desk, and they did nothing about it. It was absoutely amazing.