From my experience - gold at the start of the year, plat now - i didn't get any tangible benefits from gold until the number of nights hit 30 (with 10 says). After that the upgrades were spotty, mostly dependent (from what I could tell) on how busy the hotel was. Most upgrades were to the Club Level floors, but it was rare that I'd get a club pass - once I hit the 40's upgrades were more consistant, with Club Lounge passes the majority of the time.

Cheers,

roman