I think it's becoming a bit clichéd and soap opera-ish. It's still miles better than most things on television nowadays, but if it keeps going the way it is I can't see established actors like Jenny Agutter and Pam Ferris wanting to remain with the programme.
I mean, there's nothing wrong with it but it just seems to lack the punch of the first couple of series, where it really deserved the calibre of actors it attracted. I wouldn't like to see it continue with tons of ex soap stars taking the lead roles, which often happens if dramas are dragged on instead of being allowed come to a natural end.