We just returned from our second DDP trip and I am certain that we would not pay for it, though for free, we like it because it really did cut down on our food costs. Here's why. It just doesn't mirror how we eat. We DO like to eat a lot, but not the way DDP is structured. This trip, we found ourselves eating breakfasts and lunches and dinners so we ran out of credits. Yet, I don't think we "broke even" because we used quite a few CS credits for lunch not breakfast. Now, I could easily skip breakfast, but that's harder to do with kids.
For me, the biggest issues with DDP are (1) the credits are based on eating 2 meals a day, not 3 and (2) you HAVE to get desserts with every meal. I have basically no interest in QS dessert and when eating table service, IRL, we tend to get appetizers, not desserts. I wish you could select whether you want appetizers or desserts. I like dinner ADRs, so from that perspective the DDP works for us (dinners are costlier) but we could use extra credits (but don't necessarily want to upgrate to DxDP).
For our next trip, I am thinking about doing a room only discount and paying for dining OOP.