For a 8 day, 7 night stay, there is no way a $1200-$1400 discount for free dining for a family of 4 (ddp adults = 48 per day x 4 x 7) can possibly be offset by any room discount. A 40% dscount off a moderate (for the same duration) will be a max of $600 (using 40$ off $200 per night).
Free dining allows people to afford the trip more easily or actually afford the trip in general. So for those kids whose parents need it for their first trip and perhaps only trip...........I'll sacrifice a few extra choices for other people to experience WDW.
Just my opinion.
It think the people that say it is not worth it are making a comparison to a trip with no DDP and a room discount vs a free DDP. The assumption is valid if you do not intent on doing DDP and going ala cart you may be better of taking a room discount over Free DDP. It really comes down to personal preference and choice. Personally Free dining is the better choice for us since we would do the character and sit down meals anyway. I do miss the DDP the way it was the first time we did it in 2005, app, meal, desert and gratuity included.