I actually spent an evening (yes, I have no social life) just me, my calculator, and the WDWIG menus section to see whether it was worthwhile to purchase the Q&C vouchers. This is what I found:
Didn't do much research on the Breakfast vouchers, but it seemed to me that most of the buffets were cheaper than the vouchers, making these not a great bargain.
The Quick and Casual vouchers will almost always save you money IF you would have ordered all the things you get with the voucher (an entree, a sidedish--if not included in the entree, a drink, and a dessert). Sometimes, though, that money is merely pennies. In some cases, the deals were outstanding--at those places marked on mousesavers. If you have a big enough appetite, or 2 people with small appetites, you'll do well with them. Normally, I don't get dessert with lunch, and in most cases eliminating that from your cost would make it cheaper to pay cash than to use a voucher.
The Lunch Sit-Down Meal vouchers, I didn't have time to sift through them. The next evening I'm bored and feel like feeding my disney obsession, I'll probably do an analysis for that too.
I'm kinda playing with the idea of making a Vouchers Info Page that is more thorough than the mousesavers one...maybe including what people who've used them in the past have experienced. I'll need a few bored evenings for that, I think. LOL
BK