We never arrive before midnight and we have had VERY good luck getting our requests. I do not use the online check-in request function, I much rather call and have them added to my reservation and then follow it up with a fax 6 -7 days before check-in. The thing about being on DIS, you read about how many people ask to change their room, but I totally believe that 99% of people checking in keeps the room they get when they check-in.