What can you say about this all-time classic that hasn't been said? Or, more to the point - how you stop admiring the great story, guest cast, direction, music, and so on?
The scene with the Cybermen awakening from their slumber and breaking out of their tombs is a defining moment in Doctor Who.
I really like the continued use of electronically treated voices and the little "slot" that opens up when they speak. Very creepy.
And lets's not forget how wonderful Patrick Troughton was in this one.
SeaDevil