Tipping for a Room Upgrade

[RunDownHouse]

I was just having this discussion with somebody at work. Neither of us have ever tried it, so it was all pretty much speculation.

Can you slip the guy a $100 at check-in and get a nice room upgrade? How nice of an upgrade would you get for this, and would $50 do the job, or would $200 result in a significantly better room? Is it easier or more likely to happen at a casino like Bellagio/Wynn, or Luxor/Paris? I'm assuming it would be easier during the week/winter than on a weekend/summer.