If you follow these DDP "rules" you should always be ahead even factoring out the price of the CS desserts (which I didn't particularly want each day, and skipped all but a few days on my trip. I did have Mickey Ice Cream bars with my CS lunch at the waterparks though!!).
1. Always use DDP Adult TS credits on DINNER.
If you want to book a Character BF or 2, pay OOP because an adult CBF is 18.99 for most of them (much less than the cost of an average dinner).
Note: If you want to use your Adult TS for Character BF's, you likely will not come out ahead on the day (but it should still be within $7 of the daily plan cost).
2. Addendum to #1: If you have kids with you at the Character BF use their Child TS credits for these meals while you PAY OOP. This is because a child CBF is usually 10.99 (while child TS dinner is usually $7.49). Of course you will have to pay OOP for 2 of their TS dinners during the stay if you do this.
3. Never (repeat Never) use 2TS for any meal.
4. Always use CS credits on LUNCH.
Same principle as #1, but this time since lunch costs more on average than breakfast.
5. Use snack credits on BF items, not snacks. Most items under $4 qualify for a SC. You can get a nice coffee roll or mickey muffin at MS Bakery, Boardwalk Bakery or Starring Rolls each morning for a snack credit. Use another credit to split an OJ, pay OOP for a coffee and you'll be set. Since you get 7 SC's each, you should be set for BF for about 4 days using the SC's in this way. The days you aren't using SC for BF items pay OOP or go to a character BF and have some fun following rules #1 and #2.
Those are the basics I have followed to get the most "value" from the DDP. My last trip I followed them to a T and figured I saved about $230+ for a family of 2 adults and 1 child.
DISclaimer: All "rules" have exceptions. Look over the menus, see if a restaurant appeals to your tastes, look at the prices of items you would order and go from there. Don't base the value of the DDP on the most expensive item you can get, just the items you would order. Don't let the DDP dictate how you eat. Factor how you eat and then see if a particular DDP will work (or not). You don't have to do it. And finally, you don't have to come out ahead every day to come out ahead overall.