I have the S77S, and I think it's great. I'm not sure what the difference between the S77 and the S97 are. I can't speak for the Panasonic you're referring to, but $130 seems to be a pretty good price for a DVD player.
My only complaint about the S77, is that I swear I see interlacing on some movies, even though both the DVD player and my TV say they are getting a 480p signal. I hope it's just some kind of weird software glitch.
But I'm sure I'll be getting a HD-DVD player before too long, so this one is definitely serving me well in the interim.