I won't touch the dining plan. I don't like the way it forces me to order (must get entree and dessert, must order all three courses on deluxe, etc. Of course if you don't want the dessert you don't have to order it - but you've already paid for it, and you won't get your money back if you don't.) Back when there was only one dining plan and it included appetizers and gratuities, it was kind of silly not to use it. Now? It really depends on if you like the idea of prepaying and meticulously planning all your meals or not. You can save some money on a dining plan if you generally eat the way it is set up, but if you don't (you share meals, you skip meals, you like appetizers, etc) it gets harder.
Obviously no one NEEDS to do a dining plan if they don't want to. But some like having their meals paid for, some like going to the restaurant and being able to select anything off the menu without thinking about the price, others are going to buffets where everyone would pay the same price anyway. It's even possible to save money on the dining plan if you work it correctly (and it's more difficult to do that now than it used to be in some cases.)
And you can spend an entire Disney trip never once eating a burger, chicken or pizza if you know where to go.