To improve the twitter.com experience for everyone, we've been working to take back control of our front-end performance by moving the rendering to the server. This has allowed us to drop our initial page load times to 1/5th of what they were previously and reduce differences in performance across browsers.
Surprising no one that I am the kind of guy who would say this: I told you so, Twitter.
The rest of the Twitter post explains why #! URLs are not the best solution for rendering content quickly and consistently. Sadly, not every type of Twitter page will see this update as I noted last week:
Congratulations to Twitter for making parts of its site five times faster than its broken implementation.