Now this is us, so this may not be so for everyone, but I can't imagine ordering whatever we wanted and being at less than the dining plan. We're big eaters, particularly my DS, and we like the expensive stuff. I've never not been ahead on the dining plan. We do order things on the dining plan we wouldn't if they weren't included, but it's because we don't want to pay for it, not that we don't want it or won't eat it. Yes, our tips are higher with it, but not enough to negate the value for us. We budget for the tips, just like we budget for extras like alcohol and OOP items.
I used to be able to get value out of even QSDP, but the current incarnation seems to have made that very difficult even for me, although that might not be true of next year's plan. We're going in December, and I ran numbers for DDP, and we were definitely ahead, so I booked it. I am going to upgrade to DxDP when I pay our balance, at least partly since we ended up with another ADR, and since we're only two nights resort stay, it made far more sense to me to just add it, rather than paying $100+ OOP. That DxDP will be whimpering for mercy by the time we're done with it.
But... A)We enjoy eating that way. B)We also appreciate the challenge. C)For the way we budget, pre-paying is a major advantage. This is a stretch for us, and in order to make it a successful one, we need to work every angle. We took a trip without it once, and of course it coincided with a couple of unexpected expenses. The results have been dubbed "the cranky mommy dining plan". We are not doing that again, even if we could probably technically not starve on less than the cost of the dining plan.
It very, very much depends on your family and your eating habits. None of us drink plain tap water as our primary beverage with meals. DS and I might have mineral water instead of soda or wine. I'll occasionally order an appetizer as a meal to save money, particularly if I want dessert, but it's to keep the bill down. If one of us decided they'd rather have the vegetable pasta than steak or fish or seafood, the rest of the party would start suspecting an alien invasion. Yes, we want the snacks. And dessert too. So it's not particularly onerous to maximise the plan, and often doesn't really require a lot of thought.
But that's for my family. It doesn't work that way for everyone. If it's a good match for the way you eat, it might be for you.