As all the other reviewers cover well, this is great acting, good dialogue and strong plot. Yes is sags slightly when the unnecessary extra monster appears, but most of the real monsters are humans - the ones that help the daleks and the ones that profiteer from the situation.
Not only does the strength of the cast / script shine brightly 40 years later, but for me the passage of time has helped make the 60's East London Docks seem more strange then they could ever have seen at the time and I find myself moved by the discontinuity of the unreachable past posing as the future yet to be.
Oh and it's a lot better than the film!