I'd agree that it depends on your situation... For me, I value the diamond desk as the best reason for being diamond. I don't use them that often, maybe every 4-6 months or so, when I try to schedule a difficult/last-minute vacation stay or business trip when the hotel is sold out. It's nice to know that they always have room for me, although the price they want sometimes is expensive.

The other benefit of being a diamond is the room upgrades, as I've found you are much more likely to get a nicer room as a diamond vs. as a gold. However, as the previous poster said this is of little use if you stay at Hamptons or HGIs a lot.

The bonus points as a diamond I see as just being a secondary benefit, although it does make the points add up a little faster.