I just want to note that you might want to take the Unoffical Guide reviews with a grain of salt. Everyone has certain likes and dislikes and even though I love that book and use it all the time I have found that they are usually hard on places to eat.
We did have a bad meal at Sci-Fi., but that place has it's fans. Here's what we like. We like the commisary for breakfast, always fresh and hot. We like the area where they have little stands, there's a fresh fruit place and I think Rosies is there too. We also like 50's Prime Time.
MGM doesn't have a ton of choices, but the ones they do have are a notch above most non-WDW theme parks.
What I do with reviews is read them, but keep in mind what one person likes or dislikes may not match what I like or dislike. Plus you have to take into account that ALL restaurants have off days, even in WDW. If, however, I see 99% bad reviews and the guides books are giving it a thumbs down, it's usually a good sign to stay away. LOL
We like to pick places we've never tried and then form our own thoughts. We also have a ton of old favs. I will also try and compare notes with other DIS'ers and if I find some people that liked the same places I did, I can count on there reviews to be more accurate to my likes/dislikes.
Good luck with your choice. Out of all the places at MGM I'd probably go with 50's for the PS or Mama's. If it's just adults and your not on a super tight budget, then look into the Brown Derby.
Pam