It's pretty much all explained in this blog post: http://37signals.com/svn/posts/3112-how-basecamp-next-got-to-be-so-damn-fast-without-using-much-client-side-u

It's pretty much all explained in this blog post: http://37signals.com/svn/posts/3112-how-basecamp-next-got-to-be-so-damn-fast-without-using-much-client-side-ui http://37signals.com/svn/posts/3112-how-basecamp-next-got-to... Quote: "[...] one of the key arguments for a rewrite was that we wanted a dramatic leap forward in speed — one that wouldn’t be possible through mere evolution."