I was already rather familiar with this one, or at least the first episode. It formed part of the pre-Day of the Doctor playlist at the fiftieth anniversary party I hosted, and I once did a presentation at university comparing the first five minutes of this to the first five minutes of Rose.
My memory was that the latter three parts were rubbish compared to the first, but having watched it again, I think that’s a little harsh. They are noticeably less successful, but entertaining enough in themselves.
You can’t beat that first episode though, it’s absolutely flawless as an introduction to the series. I can’t imagine how mind-blowing it would have been at the time when Ian and Barbara first step into the TARDIS. The viewer would have had exactly the same “but it’s bigger on the inside” revelation as every companion ever.