Absolutely my favorite Cybermen. Their rather clunky, primitive costumes are actually quite effective really - stocking faces and all. They show how these first Cybermen really are us in ways subsequent versions didn't do as effectively with their helmets and metal suits. The voice modulations were very creepy as well.
The serial itself was very good, with William Hartnell being spot on, I thought.
I thought the regeneration was a well-done, mysterious affair - unlike any that followed, with the buildup that something was wrong, Ben and Polly rushing to get the Doctor back to the TARDIS, the flashing lights and TARDIS sound effects, and so forth. Highly dramatic, for the uninformed first time viewer, it must have been truly shocking to see him die and change.
One of my very favorites.
SeaDevil