I'll throw in my $0.02 based on my experience. If concierge is within your budget and you place a value on being pampered and made to feel important, then it is by all means "worth" it. It started with the rock star treatment when we boarded...we were whisked right past the line of "civilians" waiting for their picture, given the next available photographer, and then personally escorted to the concierge lounge. We really enjoyed that part of it, and it was things like that over and over again for the duration of the cruise. Pretty much snap your fingers and a team of people will do what they can to fulfill any reasonable/legal request. And keep in mind that if a cabana is high on your priority list then concierge is your best shot there.
If you're considering it just for tangible things like food and beverage, I think you could do much better skipping concierge and paying for things as you go. The concierge lounge was a very nice perk, but my kids didn't like the snack offerings unless they were coated in chocolate. I could have given them a $100 budget for Vannellope's for the week and they would have been much happier. In terms of alcohol, I think my wife and I drank about 12 glasses of wine and 5 mixed drinks total...so let's say that has a dollar value of about $150. Given that we paid about $2,500 higher for our Cat V than we would have for a 4A, if you're just thinking about it in terms of dollar value then we overpaid by a factor of 10.