My opinion, and I share it all the time when this comes up, is that the dining plan has everything to do with one thing... CHARACTER MEALS.
My wife and I went to WDW three times w/o any kids and basically paid for the Crystal Palace breakfast and WCC as our only sitdowns all three times and were just fine. We just ate at the counter service places when we were hungry. This was much, much, much cheaper than the dining plan for sure. Plus, I really do think the counter service places are underrated and offer much more than just burgers. And just as a side note... I LOVE TO EAT!
Then we took a few years off after our daughter came along and went in 2007. We also went with my parents, brother and niece. I was going to do the usual, but my mom really wanted to try the dining plan so we did. To say our daughter LOVED the character meals is an understatement.
We are going in June and booked the plan mainly for this reason. We have Chef Mickey's Din , 1900 Park Fare Din, Play-N-Dine B'Fast, Tusker B'Fast, Crystal Palace lunch and Akershaus B'fast character meals, plus Biergarten Din for us.. (plus she liked the show there last time.)
That's alot of characters, but if you think about it we 1. like the food at all those places so there really isn't much of a sacrifice and 2. get to see... Cinderalla, Prince Charming, the step sisters, Mickey, Donald, Pluto, Goofy, Belle, Mulan, Jasmine, Pooh, Tigger, Daisy, Jo Jo, etc, etc, etc. That would take a looooooonnnnnnnggggggg time to track all those guys and gals down in the parks for autographs, which are not really an option if you know what I mean!
So for us this does actually save time, especially with late breakfasts, early lunches and strategically placed dinners. You can really make out just doing breakfasts and lunches if you can, but for us we couldn't (Cinderella is a dinner only at 1900 Park Fare for instance).
Now, if she was a little older we would probably skip the dining plan and eat on the fly and a select few sit-downs because they do take up time and (especially dinners) can impact your day.
There is no way we'll get tired of the character meals just because she loves them and is the kind of kid who stalks characters at home. Critters like Chuck E. Cheese, the Pirate Parrot, Steeley McBeem, Ricky Racoon and Kenny Kangaroo (Pittsburgh folks know all these guys) have to hide from her. She literally tip-toes behind them giggling. She's in her element BIG TIME at the meals so like I said, it saves us time.
Just my personal thoughts.