For us, the premium or platium plans would only make sense for an adults-only trip, when DH would be golfing every day, I'd be taking tours and hitting the spa, and we'd be doing more of the recreation. With the kids, we're too parks-focused for the plan to make sense. I don't remember the per-night price on the premium plan, but it was a LOT more than the deluxe dining.
To give you some idea - DH is golfing twice on this upcoming trip, we're leaving the kids at the Cub's Den one night, playing mini-golf once, doing the steam trains tour at the Magic Kingdom and probably the Behind the Seeds tour at Epcot, going parasailing if the weather cooperates, renting SeaRaycers one morning, and I added in Cirque tickets for comparison's sake because we were thinking about doing it. All of that out of pocket on top of the cost of our deluxe dining package is still cheaper than paying for the premium package.