Only you can really decide if it is worth it to you.
For me it is very much worth it. I have used the get a diamond guarantee room when hotel sold out many times, and no, never had to pay rack rate for the room.
Diamonds get reduced point rewards, got one for spring training in Phoenix in March, normal rate 75,000 per night, Diamond rate 30,000 per night for the Doubletree.
Have used my points for some great vacations at wonderful hotels throughout the world. Being Diamond I earn points much faster so can get those vacations annually.
So for me, well worth being Diamond. And sometime next year will qualify for lifetime Diamond.