I was so Happy that they did that! DOTD was EXCELLENT!!!! I can't wait to see more of Season 8!
It also raises the question "Can the Doctor regenerate back into a previous version?"
And yeah, I got excited when that happened (Trying to avoid spoilers for people here).
I loved all the nods to the past 50 years. Even the school that Clara was teaching at - it was in the very first episode of Doctor Who 50 years ago.
I've been playing the 50th show on a loop in the store all day.
I'll admit I've never even watched a single episode in my life.
It's not for everyone, but if you wanted to check it out, start in 2005. 2006/07 was some of the best written TV I've ever watched, and the way they interweave the storylines all the way through to 2012 is amazing.