Wonderful talk. One of the things Bartle repeatedly mentions is that when designing, you need to know WHY you are doing it in the thing that YOU are designing.
Not because someone else has done it, not because everyone ELSE is doing it, but because it has a definite purpose in YOUR system.
Also has a great rant towards the end about how people don't do things better, because they don't realise that they can - that they're allowed to.
Some great quotes:
I won't be telling you how great text is over graphics, because that's an argument I've won many times... and still lost.
I won't be telling you how great permadeath is - God uses it, it can't be bad.
It behooves you all to understand WHAT you are designing, and WHY you are designing it.
What we wanted to do was say unpalatable things about the real world - within the protective frame of a game.
You must understand what's in the paradigm - then you can throw it away.
We put in the level system because it let you OUT of the (British social) class system!
Much of what he says isn't specific just to game design, but to learning and perfecting any craft.