First off, the description is wrong, this is only a 2 disc set. There has never been a 3 disk version available. Outside of that, this is a great story. The Doctor (William Hartnell) and his companiions Ben and Polly arrive in Antarctica in 1986 just in time for the Cybermen to arrive on Earth.
The special features, like all Doctor Who DVDs are extraordinary, including production notes, commentaries and much, much more.
Sadly, most of the final episode does not exist in the BBC archives, so it is represented here as an animated form, alongside the version released for video cassette many years ago.
I highly recommend this to any fan of Doctor Who, or for someone just getting into the 1960's era of the show.