We got the dining plan for free during the special promotion back in October, and we loved it. However, if we had to pay for it, it would end up costing us a little more than we usually spend, for 2 reasons: 1)we usually budget $25-30 per person per day for food, compared to the $38 the plan costs, and 2)we'd have to give up our AP or Florida Resident room discounts to use it.
If it weren't for the room discount, I would probably go ahead and buy it anyway, since the plan was so much fun to use. It made us feel free to eat wherever we wanted and not worry about how much things cost when we order them (not that we usually are biting our fingernails about that, but we do budget and put some thought into staying within the budget). However, it's just not worth giving up our room discount for. We're going with the DDE next time instead, which we're eligible for since we're passholders.
I would say if you're going to be paying rack rate for your room anyway, then the plan will probably be worth it, but if you could get a discount on your room, then you should just crunch the numbers by how much you would spend either way to decide if it makes sense for you.