We had a great meal at Hollywood Brown Derby but in my opinion it's not worth the $$ for a signature meal. We tried Mama Melrose and although it wasn't amazingly good (just like a local Italian restaurant) it was good especially on the ddp on the Fantasmic package where you get the three courses. We did like Sci-Fi though - still nothing exceptional but the theming is great although my DS had issues with not being able to see his food clearly
We do think that DHS and AK are the weak links for food at Disney. Would prefer to leave DHS and walk to the Boardwalk/Yacht and Beach for food :