Funny, DH and I were just talking about whether is was "worth it" to us. We've sailed twice on the Fantasy, once in a regular family stateroom w/veranda, and more recently in the concierge family stateroom w/veranda. What we most appreciated about concierge was the shoreside assistance we got with pre-booking Remy and spa appointments and cabanas, and of course being able to do it 120 days out. On the ship, we took advantage of the concierge lounge quite a bit, and it was wonderful in the mornings to be able to pop down the hall for some good coffee and a plate of pastries to bring back to the room. We LOVED having a cabana on CC and that would never have happened had we not been concierge. Beyond that? We either didn't really take advantage of any perks, or else we didn't find them to be superior to what we experienced when we weren't concierge. Our conclusion was that we would probably pay the premium on a future sailing IF it was during low season and not too exorbitantly priced, but we won't do it if we sail over the holidays next year because nothing we experienced would justify that sort of a price hike.
I think I'd feel differently if the stateroom we stayed in was bigger than what we had before, but it wasn't. It had nicer decor and a few extra touches, but for the most part, it was the same room, just with concierge perks added on. Had we been in a one-bedroom, I'd probably have been more wowed.