I have been a Global Hotel Alliance (GHA) Black member for the whole of 2015 and I have had a lot of upgrade successes (more so than most international hotel chains) at a number of properties worldwide:
According to official benefits set out by the Global Hotel Alliance, Black-tier members should get early check in from 9AM, late check out until 6PM, guaranteed room availability up to 24 hours prior to arrival, a double room upgrade and a personal choice of local amenity. What is impressive to me (especially in the capacity of a staycation-goer) is the early check-in and late check-out. Considering how most hotels allow you to check-in at 3PM and check-out at 12PM (21 Hours), having the Black status will effectively increase your hotel stay from 21 Hours to 33 Hours (effectively 57% more time in the room or suite!).
I really loved my GHA Black benefits and you used to be able to early qualifying nights even on OTA rates but ever since 2015, you were only able to earn eligible nights when you book directly with the hotel - I have had issues when I booked via GHA itself too (strange!). Upgrade successes were always high and checking-out late is always a breeze (unless at full occupancy of course) but unfortunately, I was not able to hit 30 eligible nights this year so I will be back at Platinum next year which isn't too shabby after all.