This is one of our (me, DH, two DS's) favorite places to eat at WDW. The theming is fun - car tables facing a "drive-in" theatre screen. Yes, they show the same clips over and over, but it's a fairly long reel of clips. We don't eat all that fast, and most of the time when we finish our meal the clips are just starting to get to the point where they were when we got there. This last trip we finished eating before the clips started repeating.
I highly recommend lunch over dinner. The food here is not spectacular overall, but the burgers and shakes are delicious. The burgers aren't on the dinner menu though, and although you can order a burger off-menu they aren't as good as they are at lunch (I'm speaking from personal experience and from posts by other people who have done this).
If you go into it expecting a fun, campy setting and stick with burgers and shakes for lunch, I think you'll enjoy Sci Fi.