Welcome to the Dis!
If this is your first trip, I'd go with the regular dining plan. The reason for this is that the deluxe plan will take up too much of your time away from the parks. How long are you staying? Are you going in 2008 because the deluxe plan doesn't take effect until Jan. 2008.
Although it doesn't seem like a lot compared to the deluxe plan, most people usually complain that the regular dining plan offers too much food let alone the deluxe plan.
With the regular dining plan, each person gets 1 counter service meal which consists of a entree, dessert and non alcoholic drink per night, 1 snack per night and 1 table service meal per night which consists of 1 entree, 1 dessert and 1 non alcohoclic drink. This includes buffets and character meals.
For example, if you stay for 5 nights, 6 days, each person in your room will get 5 counter service (fast food) meals, 5 snacks and 5 sit down meals/buffets/character meals.
You can order whatever you want from the menu. Very few restaurants have small restrictions.
The deluxe plan is basically the same except that it offers 3 meals per night and they can be either counter or table service meals, plus 2 snacks per night per person. You also get a free refillable mug which I think is wonderful especially if you drink a lot of soda or coffee and the deluxe also offers appetizers where the regular DP doesn't.
Either way, you would only get the best value if you did your research in advance and found out which restaurants would be best for your group by looking at menus and ordering the more expensive stuff.You would have to make reservations in advance too and not all disney restaurants are on the plan. If you have picky eaters in your group or you don't eat much, I'd defenetely go with the regular DP. The deluxe would take away a lot of time from touring the parks.
One last thing to note...you can exchange 2 regular table service meals for a signature meal (aka very expensive fancy restaurants), or a dinner show if your interested in that.
Here is a link that might also help with more info and the participating locations that accept the plans:
http://allearsnet.com/pl/packages07a.htm