I can only give reviews for the couple I've been to, but here are my thoughts:
Biergarten - One of my family's favorites. To get the best value, go to lunch if paying out of pocket or dinner if on the DDP, and watch for showtimes if you want to time your ADR with the band, Oktoberfest Musikanten (schedule the ADR for 30 minutes or so ahead of the show). If you enjoy German food - brats, sauerkraut, spaetzle, pretzel rolls, etc., it's terrific. There are some more typical American foods on the buffet (e.g., plain chicken, mac & cheese) for the less adventurous, although if you don't enjoy the flavors of German cuisine (think cabbage, root vegetables, hot and cold sausages, caraway, dill, vinegar) the food may not appeal to you. As for us, this is the one ADR my husband requests every time we visit! Do be aware that the tables seat 8 or more, so if you don't take up a whole table you'll be seated with another family, European-style.
50's PrimeTime -- a fun place, especially for lunch, and a good value out of pocket for classic American fare and fun retro decor, especially if you're willing to play along with your server's reminders to keep elbows off the table, etc. Ask to be seated at one of the "TV tables" and tell them you're willing to wait a little longer for one to open up, if necessary. It's well worth it.
Hollywood and Vine -- I can think of better ways to get a good seat at Fantasmic. If you have little ones who are obsessed with Disney, Jr., characters, you might consider it, but food-wise, it's far and away the worst dining experience I've ever had on Disney property. Bland food, all served tepid and either over or under-cooked in a cold and clinical cafeteria setting, and although I'm the opposite of a picky eater, I couldn't find a single thing to like. It was all-you-care-to-enjoy, yet my party of 6 couldn't wait to go and get a treat at the ice cream cart afterwards, because everyone was
still hungry.
Be Our Guest -- Had lunch there and it was the best counter-service meal I've ever had on property, with better-quality ingredients and nicer presentation than typical counter-service. Lovely theming, efficient and fast service, with your choice of ambiance (quiet and dark in the West Wing, loud and airy in the Ballroom).