I like the dining plan. I liked it a lot better in the past because now the tip is not included. With that said, what I did when I was trying to figure out if it was worth it, I went to allears . net or go to wdwinfo, and looked at the menu.
Since it had prices there, it is easy to figure up about how much you would be paying out of pocket. If it averaged out less than the dining plan, then I would go with it, if not, then I'd skip it.
It also depends on what you like to do while there. If you are going for the parks and to spend the most amount of time in the, then you may not want to take time out for a meal every day. Counter service will be a lot quicker and take up a lot less time. For me, eating out and trying new places is part of vacation, so I like to eat at a sit down place every day.
Just my 2 cents worth.