twhirl is a Twitter client based on Adobe AIR. It is a cross-platform app with a very nice look and a bunch of interesting features for you to manage multiple Twitter accounts and also get news feeds from identi.ca, laconi.ca, and Friendfeed. It also integrates with Ping.fm, giving you the chance to distribute your tweets over other social networks like Facebook.
The nice part of using a client for Twitter is that you don't need to go to the web to check what's going on. Instead, while you're working or focused on something else, you can be notified instantly of all the news and updates of your interest. And twhirl uses an efficient notification system that alerts you with a sound and fancy Growl-like messages whenever you get new tweets, mentions, replies, etc.
To access your accounts from twhirl you just go to the 'accounts' tab, select the service, and add your login credentials. Once connected, you will see that from the app's small window it is possible to do just about anything you do in Twitter. Apart from checking direct messages, mentions, followers, and of course, tweeting, there is a filter where you can track words or users in your timeline. One of my favorites features is the search functionality, which allows you to follow a specific topic of conversation using Twitter Search or TweetScan, letting you save your searches and integrate them into the timeline. You will also a find a URL shortener (with 4 services), the possibility of sharing images via TwitPic, and support for Seesmic video.
A broad range of options is available from the settings, enabling you to customize the notifications, set the app's transparency, use the spellchecker, change the app's colors, etc.
twhirl is a very complete client and has a neat, compact interface that doesn't take over your desktop. It does lack, however, advanced functions that you can find in TweetDeck or HootSuite, such as the possibility to schedule tweets or the use of columns to separate tweets, replies, mentions, dm's, and other functions which can also serve marketing purposes. Ultimately, your choice depends on the use you make of the microblogging service. As for myself, I'll stay with twhirl.