Agree with Wendy about Ponderosa - it was great the first time I tried it but now I think it's a yucky place.
Shame about Marrakesh Sandra as that is one of my best. I however, would have to be dragged kicking and screaming back into the Sci Fi Diner.
Have to also say that after the last experience at 50s Prime Time I won't consider going back there again either. Dining plan has ruined that place - no time for fun now, it's all serve, serve, collect tip, serve.