I've run the math, using $3 as a snack credit value.
For 2010, the "break even value" for the dining plans are: a snack is valued at $3, an adult CS credit is $13, an adult TS credit is $26 ($32 peak), and an adult deluxe meal credit is $22.
For 2011, the "break even value" for the dining plans are: a snack is valued at $3, an adult CS credit is $14.50, an adult TS credit is $28.50 ($30.50 peak), and an adult deluxe meal credit is $24.33.
Note these are on average, so don't feel like you're cheated if you have some meals/snacks at a lesser value, unless you're doing so often enough to bring your average below breaking even.