An interesting (and wonk-ish) post by John Gruber discusses how the newest official Twitter clients might betray a shift in thinking among the service's masters. There's also lots of good general stuff about twitter clients, with thoughts on the way their use can change the experience compared to simply using the service via the twitter.com web page.
"…these changes suggest not only a difference in opinion regarding how a Twitter client should work, but also regarding just what the point is of Twitter as a service. The Twitter service I signed up for is one where people tweet 140-character posts, you follow those people whose tweets you tend to enjoy, and that’s it. The Twitter service this new UI presents is about a whole lot more — mass-market spoonfed “trending topics” and sponsored content. It’s trying to make Twitter work for people who don’t see the appeal of what Twitter was supposed to be."