Three AIR-based Twitter apps: Spaz, Snitter, and Tweetr
I've been experimenting with Twittercasting live Web news lately (see Facebook press conference and Web 2.0 Summit reports). But I found doing so from Twitter.com itself a little tedious. So I went searching for desktop Twitter applications. Previously I've used Twitteroo, which is solid if light on features. But there are new Twitter apps being written for Adobe's AIR platform. Here are three that I've tried and like.
Spaz, Snitter, Tweetr. Gesundheit.
Spaz is a great-looking Twitter client, to my eyes the best of this bunch. I think it has the best interface, with tabs for your timeline, direct messages and replies, as well as access to your list of followers and followees. It's a little buggy (sometimes it doesn't retrieve the data you ask it for), but not bad considering its stage of development (version "0.2.9").
Special power: Looks great.
Oops: Bugs.
Snitter is more robust than Spaz, and faster, too. It gives you reliable access to all the Twitter streams you'd want, including the "replies" stream of Twitters from users replying to your messages even if you're not following them (it's hard to find this stream on Twitter.com itself). It can also display little messages when Twitters come in. Surprisingly, getting these Outlook-like "toast" pop-ups is a lot less annoying for Twitter messages than emails. But while the application itself is fast, switching between streams requires a selection from a drop-down menu--tedious. Update: See comments. There are keyboard shortcuts for the menu.
Special powers: Reliable. Fast.
Oops: UI shortcuts not obvious.
Tweetr doesn't display your list of friends and followers like the other two apps, but it does have a unique feature: It lets you snap pictures from your Webcam, or upload files by drag-and-drop. It creates short URLs that you can then send out immediately to your Twitter friends. Example. (See also: Twittergram and EyeJot.) It also displays "toast" pop-ups. I found it slow to display content when switching feeds, though.
Special power: Webcam integration and file uploading.
Oops: Slow.
The best
My pick of these apps is Snitter, by a nose. In side-by-side usage, I just found it loaded data the fastest, despite its kludgy feed-switching interface.
Bonus tip: If you have multiple Twitter accounts (like I do: my personal feed as well as event-specific feeds), you can use more than one of these apps at a time and point them to different Twitter accounts. Or use Twitter.com for one account and an app for the other. Trying to open an AIR app twice just re-opens the first instance.
Rafe Needleman writes about start-ups, new technologies, and Web 2.0 products, as editor of CNET's Webware. E-mail Rafe. 
The shortcoming in snitter that you describe, that stream-switching requires the drop-down menu, isn't actually true:
From http://snook.ca/snitter/
Features:
[http://...|http://...]
keyboard shortcuts to access each panel (t=tweets, a=archives, r=replies, d=direct messages, f=favourites, i=friends, o=followers, u=updates)
Much better and faster than the drop down. Does that give snitter a bit more than a nose across the finish line? I've been using it for a few days, and haven't tried the others, but I like snitter a lot.