Hiya, we had the dining plan in sept and it was great! Yes, it's expensive but you get to eat in some great disney restaurants that would have been out of our price league if we hadn't had the plan.
We had DH, me, DD aged 10, DS aged 7 on the plan so it worked out at 3 adults and 1 child. We were a bit confused with it all at first - as we found out everyone is!! LOL! However, most of the servers were great, explaining exactly what we did and didn't get included. The only one's I found a bit lacking were the counter staff in Disney Quest.
Notably good service came from Crystal Palace, Ohana, Chef Mickeys - all character breakfasts; Le Cellier - most expensive meal we had - $195 - server recommended the special as it was included in the plan - Lobster and Steak!!!, Boma - really good food, great choice buffet for everyone; Cali Grill - Great setting, food good, and server (Hi Gary - ex Marine served with the Para's) - helped us get good value out of our plan. DD didn't always want a starter, and most servers queried this as we were missing out on free food - we just explained it wasn't a problem and we knew it was included but it didn't matter. I'd never thought of it all affecting their tip!! When the service was really good we left a tip on top too.
Counter services were adequate, some better than others. The food court at CBR was good, and the staff there were helping everyone on the plan so they didn't miss out on things.
Only hiccup we encountered was in AK Pizzafari, DS didn't like the 2 kids choices, so we opted to get him a pizza from the adult menu, but this wouldn't go through as 4 adult meals on the till. I asked the server if I could charge 3 meals, then charge the other one seperately, and this was fine.
The other thing to watch for is some counter services don't have desserts included but this isn't indicated on the menu, Earl of Sandwich was one - a very confusing counter system, but good food! Also watch for the sizes of drinks included - usually the bottled ones, you should get large ones most of the time.
The plan certainly helped us have a greater experience in WDW, and it was well worth it. So don't worry about it at all, if you need to just ask, they're so helpful over there. And if there are any discrepancies query it with them, the americans do!!
And we left with about 12 snacks remaining - we couldn't use them up as we were getting fruit, cookies, yoghurts as desserts with our B/F from CBR and keeping them in our room fridge!!