There's two giant components to public speaking: (1) not freezing up and (2) successfully communicating what you want to communicate. Well, really, those are the two components to any form of communication. For most people, this is circular: they freeze up because they don't think they can communicate, and they can't communicate because they freeze up: so learning public speaking is a matter of breaking that cycle on either end.
Your speeches are good if you got your message across. Sometimes that requires getting a laugh. Sometimes that requires a plot twist to make them reconsider. Sometimes that only requires reciting the facts without embellishment. It depends on your audience and your relation to them. A "master key" that doesn't recognize that you can't give the same speech to a group of 5 year olds that you gave to a group of Nobel laureates is useless.
Also, James Mickens in the systems community (and also a colleague at MSR) is really good. He tends to go off the wall a bit more, but that is just part of his rhythm.
I guess it's subjective...
The point of TED talks isn't that they're supposed to have a stand-up comedian's level of presentation skill. It's about captains of industry talking about their slice of the world.
It turns out that my first speeches weren't very good. I didn't understand that writing and speaking are different. When it clicked, I wrote: "I have deciphered the master key to public speaking: use Vanity (idolz) or Pride (topic translatable to lowest common denominator), but not Envy (my endeavors)."
So in my opinion, TED by nature of being oral presentations would skew away from the dry wit, and piercing insight of writing.