Its huge.
Its got Sonny Eclipse, the audio animatronic lounge singer (who sings constantly - it isn't like Chuck E Cheese where there are only occational shows). I'm not a huge Sonny fan, but my kids (2 and 3 when we went) were. We'd eat, they'd dance. The restaurant isn't as heavily themed as a Rainforest Cafe - its a Tomorrowland restaurant, so think "sleak modern".
It ridiculously close to Fantasyland, tucked between FL and Tomorrowland. Which means that if you have small kids you are likely very close. (Beaches and Cream may be a lot better, but if you'd have to leave the MK and head way over to the Epcot resort area to get that burger. Probably not worth the time for most people.) Its also hard to miss.
They have huge sandwiches and salads. Plus the chicken deal. Making them not a bad bargain as far as MK restaurants go.
I don't think its worth going out of your way for. You can check out Sonny as you are walking by. But if you are next to it at lunch or dinner time, its worth it. And I agree the multi-line thing (which speeds up service a lot) makes going there with small kids, two adults, and a party that wants different things a difficult proposition. (If everyone wants burgers, its easy).