But things move fast in the iPhone app world. A new wave of Twitter apps surpassed Twitterrific in features and functionality, perhaps most notably . (It's certainly my favorite.)

Now, at last, comes : Twitterrific 2.0 for iPhone, which has been approved by Apple and will likely be released on the App Store Friday. It will be a free upgrade for all existing users. New users can download a free version, which includes ads, or pay an introductory price of US$4 for the ad-free premium edition. I've been testing this version for a few weeks; here's a hands-on first look.

The first version of Twitterrific was obsessively focused on streamlining the reading experience. That philosophy still underlies this version, but layered on top are a zillion and one new features that exploit the growth of Twitter and the increasing power of the system app developers use to connect with Twitter.

The app's tweet-reading view looks pretty much the same as in the previous version, with the exception of a new toolbar on top (which allows you to toggle between large, medium, and brand-new teensy type display modes, as well as open the new Sources screen). The big change is on the bottom: Tap on the new filter menu (the icon looks like a funnel), and you can filter your timeline, focusing on just replies, direct messages, favorites, messages you've sent, and messages you've marked for later use.