The Fantasmic Dessert Balcony is, in my opinion, definitely worth the cost (around $50 per person). The seating is extremely limited - only 20 - 25 seats per show. The desserts are mostly "store bought" style. If you can, get the first show of the night so you can stay for the fireworks. The Riverside seating is not worth the money as it is not centered on the show and has people standing in front of you.
The Blue Bayou, located in Pirates of the Caribbean, is my favorite lunch location. However, I don't think it is worth the cost for dinner.
My favorite dinner location is in California Adventure - the Wine Country Trattoria. Make reservations for around 8:00 and ask for a patio edge seat, that way you can see the Electrical Parade as you enjoy dessert!
Other good food locations:
California Adventure: Award Wieners (ask for only the hot dog if some one else in your group is ordering the full meal with french fries); Burr-bank ice-cream; Taste Pilot's Grill (the kid's meal is huge and the regular hamburgers will serve two); San Andreas Shakes (real ice cream/whip cream shakes); Pacific Wharf Cafe.
Disneyland:
Carnation Cafe (great place for breakfast, right on Main Street); Plaza Inn (split a meal with some one - great fried chicken); Rancho del Zocalo (go to the left, to the grill - great fresh food, huge portions); Golden Horseshoe (okay, not my first choice for food, but the show is great - and you can go across the way to Zocalo to bring in better food - just get there early to get a table).
Downtown Disney:
The only place I eat there on a regular basis is breakfast at the Jazz Cafe, for fresh beignets and coffee/hot chocolate - just like New Orleans. I have also taken sandwiches back to my hotel room from La Brea Bakery.
Disneyland Hotels:
Here is my weakest knowledge (but if you really insist, I will go try out some places

). The only place I have eaten at recently is PCH Grill at Minnie's (now Lilo and Stitch) Breakfast at the Paradise Pier Hotel.
As you can tell, I love to eat! If you have any questions, please feel free to ask!