The first few years the plan was available, the plan made much more financial sense. Tips and appetizers were included in the Table Service meal. My wife and I do prefer sit down meals, taking a breath and enjoying our food, so we wound up having enough extra table service credits to buy a bunch of pre-wrapped sandwiches and desserts that we ate on the 20 hour car ride home, doling out little bits of WDW every couple of hours. And my wife and I often would split a dessert and either let one go to waste, or ask a random family next to us on line, "hey, your kid want a cookie or brownie, we've got a free dessert we're not going to eat."
Now, you're not getting nearly as much bang for your buck. You can still save a few bucks on the Dining Plan, but not as much. I'd be much more keen on it if the table service meal allowed you a choice of an appetizer or a dessert, instead of just a dessert. And as others have stated, WDW has been cutting corners by limiting, AND homogenizing, the choices of food at the restaurants. By not having too many choices, they can cut back on the supplies they order, and if that means every restaurant starts to look like they're serving the exact same meals but on slightly different plates, so be it. In fact, hey, maybe when it comes to replacing the plates, we should get them all the same plates. And when it comes time to redecoration, let's just paint them all the same color, or get the same wallpaper. Heck, why not just buy bulk furniture at Ikea and get the international cast members to put it all together? Bland 'em all together so you're not even sure where you're eating. That's the sort of experience Walt would've wanted, I'm sure.
Back on topic, if you don't mind doing a little bit of homework, checking out menus and prices, I'm sure you'll figure out if the plan is worth it for you. You should, at the very least, break even, and this way most of your dining costs don't have to be a worry for you. But you may also find, depending on what you'd like to order, if you'd rather split appetizers and desserts with your family, whether or not you want TWO potentially big desserts during the course of your day (plus what could be a potentially fattening snack), maybe you're better off buying what you want as you go. Sure, there's no law that says you HAVE to eat every dessert, and that they must be awful for you. But again, you're probably not going to save much of anything if you don't, so you may decide it's better not to get the plan.