Just this week, I checked into the Hyatt Cambridge, MA at 3:00 AM on Wednesday morning, March 22. But my reservation was for Tuesday, March 21. I had an e-mail from a sales manager confirming that I would be arriving at 3:00 AM and even called the front desk on Tuesday afternoon to confirm that I would be arriving at 3:00 AM. Got to the hotel and everything was fine.
When I checked out, they charged me my regular one night plus a night's rate as a no show. I got it straightened out, but just goes to show that even with all the prep and planning, the hotel could still screw up with a late night arrival.