Watched all but the last one now. To be honest, I expected a dip in quality after the insane episode 5 based on some of the previous posts here but I really enjoyed eps 6 and 7 (has anyone seen a ropey movie called Ghost Ship? Its pretty bad but has an incredible opening 10 minutes that is reminiscent of the Panama Canal scene).
As for the actors, I think they are all fine.
I think this show does the best job of straddling sci-fi and actual real physics that I have seen. The only two stretches are the nano-fibers and the hibernation machine but I can live with that. I also read something about nuclear-pulse propulsion years ago so that to me is fair game.