I watched The Talons of Weng-Chiang
recently. I ended up watching the whole serial in one sitting. That almost always happens to me.
I enjoyed it. I like the bigger scope and sets of characters the classic serials often have. There were some really good supporting characters in this - the professor (?) with his gentlemanly though misguided swashbuckling (I really liked the dinner he had with Leela) and the director of the variety theatre. The setting was great, too.
Unfortunately, I'm out of more stories to watch in chronological order at the moment.