We stayed on the concierge level a few years ago. At that time, it was roughly $75 more per night for concierge level. We had access to the 14th floor (I think) where the concierge lounge was. There were sodas (cans) and bottled water available all day long, plus continental breakfast in the morning, dessert-type snacks in the afternoon, and wine & cheese during the pre-dinner hours, and some more desserts late night. We mainly took advantage of the sodas and the snacks, but neither of us felt it was enough value to book that level again. I remember mentioning to the concierge staff that it was my husband's birthday and asking for recommendations on dining, and they were #1 - not that helpful with suggestions (I didn't really need help - was just testing their knowledge) and #2 - they didn't send a card or balloon or anything to the room, and I was watching as they were writing up cards for other guests, so I know they can do that...
I still love the upper floor view of Downtown Disney and DL from the Sierra tower, and that is always our request, but we don't drink or eat $75 per night worth so it's non-concierge for us!