We did concierge at GCH for a trip and it was fantastic! We got a phone call a few days before our trip offering assistance with whatever we needed. There is a separate check-in, so no waiting in line. The lounge is great because it gives you a place to hang out other than your room. (For us this was big since me, DH and our two kids were all in one room.) They have storytelling in the evenings for kids, as well as games and fireworks viewing in the lounge. It was never crowded (we were there in August so everything else was sure crowded!). You're not going to get three square meals a day out of the food offerings, but you can definitely put together a breakfast. We also took extras (bagels, yogurt, water bottles, cereal, etc.) into the park with us and that saved us some time and money when the kids got hungry. It was nice to be able to stop in for some munchies in the late afternoon and then back for dessert (and alcoholic beverages) at night! The best part was this . . . we were there the summer that WOC opened. We waited for several hours to get a great view, but while we were waiting for the show to start, my DH ran back to the concierge lounge and packed up some drinks and cookies so we could snack while we waited. They also have a separate concierge desk in the 6th floor lobby, where you can borrow DVDs or get assistance with whatever you need.
Do you *need* concierge? Of course not. I like it just because it's so easy, but including the food and convenience, we've decided it's probably worth about $125 a night for the 4 of us. I think we paid an extra $100 a night and DH and I agreed it was well worth it. $150 would be pushing it. $200 - no way. That's just the value we put on it, YMMV!