I still don't understand all of the fuss. These two are close enough in performance to where people should pick the framework that best serves their needs, their designs, and their brains.
Big deal -- there are now two ways (at least) to accomplish the same outcome in Python. Competition is good. I'm guessing that this will be a call to arms for the Twisted community and we'll see development accelerate.
At the same time, it is likely that a development community will form around Tornado. Great!
It's like people saying, when the Mac OS first launched, "Why didn't they just use DOS --it's there and it works." And yet the Mac OS has had a positive impact on operating systems produced by Microsoft. And Microsoft has impacted the Mac OS. It's all good.
And why is it that this same argument doesn't occur every time a non-async framework appears for python or other languages? What is it about the async nature that polarizes people? Maybe it's the fact that the both also start with the letter "T" and the name "Tornado" is a better named than "Twisted" (which implies increased complexity even if it isn't there...of course Tornados ultimately make a mess of things, so that's not it).
I, personally, am excited about Tornado. I think there's room for more than one player -- especially given the 'real time' direction the web is heading. And if this negatively impacts Twisted, then it'll be because Tornado has come up with an easier to understand approach and they'll benefit from being new and easy to grok -- in the same way Rails was once an easy-to-grok framework and that's what made it easy to understand.
The biggest winner, in my opinion, is the Python community and who doesn't want that?