When it comes to budgeting for your trip, the dining plan can answer the question of "how much money do I bring?". But, I'm still not convinced that it is any kind of bargain. Keep in mind that the room and tickets for your trip will be at Disney's higher prices.
That means a moderate room in June will go for $149/night plus tax (rack rate). If codes come out for the general public, you could see that same room going for as little as $99/night. Ultimately, that $45/night more for the dining addon may actually cost you $100/night more than booking a room-only with a code. Suddenly the dining option is not such a great bargain.
If you have not booked a package yet -wait. Codes for the late part of April until July 4 could come out in the next couple of weeks. When (if) they do, you will have a better idea of what the bottom line will be for both a package and booking room + tickets and paying for dining separately.