For our recent WDW trip, a first for DD and me, I got some Q&C and Feature Breakfast vouchers. With both, I at least broke even although at several of the counter service restaurants listed for the Q&C there are very limited dessert options (only one for Pecos Bills and 2 at Cosmic Rays). If you don't get the dessert, I don't think you're as likely to save money. The breakfast vouchers seemed to work best for us... but we didn't use 2 because I discovered my DD wasn't ready for quite so many character meals

)) and the other options for those vouchers were not a good deal.
I have to admit that when I was researching for the trip, the vouchers really seemed like a great idea. The reality, though, was that I found the Q&C especially weren't as good a deal as I'd expected. Partly, I think this was because I just wasn't that hungry due to the heat and humidity and partly because what sounded good when I researched restaurant menus and prices wasn't what sounded good when I was ready to eat - and often what did sound good wasn't high enough priced to make using the voucher worthwhile.
If I had it to do again, I'd have bought only half as many as I did. It was definitely nice to have the prepaid meals but it almost felt like an obligation to use them to best advantage (I came home with 1 q&c and 2 breakfast). Also, because they aren't accepted at all counter service restaurants, I probably missed some good food choices that would have been more appealing to me at the time. Oh well, I don't regret getting them as it was definitely something I think you need to try for yourself to see if it is worth doing again.
100%Disney - some people have sold them on DISauctions. Unfortunately, I think that part of the site is down right now. I have seen a couple of threads on the budget board where people are looking for some to buy and others say they have extras. After that, I believe it is all transacted privately through PM or email due to the DIS policy against selling from the boards. I think they relaxed the policy enough to allow the basic exchange of information seen in those posts because the auction site isn't working.