Twitter is apparently rolling out a settings feature that allows you to download your tweets as a single download.
This won't be very useful for me since I've been manually archiving my twit-spewings for the last three years. I started doing it because the search and pageback functions were so lousy, and just kept up the practice. The tweets were supposed to be my notes and I do use the self-archive pretty regularly to find something I jotted down.