Adam,

The reason I didn't add Seesmic to this list is because its a separate social network that interacts with Twitter.  It's not an application to directly update your twitter status which is what this article is really about.  I think twirl is the best tool to utilize all micro-blogging social networks simultaneously as it integrates with seesmic, friendfeed, and several others. Another popular interface is ping.fm which integrates with facebook, myspace, and as much more features than twirl.

I hope that answers your question.