Twitter upgraded its suite of apps recently and gave Tweetdeck for the Mac a huge overhaul. Users loved the twitter client for its column-based interface and hated it for its reliance on Adobe Air. The latest version of Tweetdeck keeps the columns, but drops Adobe Air. It replaces it with a lighter, simplified interface; but that's not necessarily a good thing, especially for power users.
The new Tweetdeck is a scaled-down version of the Air Version. It has less room for columns and fewer options for each column. On my 13-inch MBP, I can only show three columns in the new Tweetdeck instead of four. I also can't filter tweets in a column any more.
Notifications are hit and miss for me as well. You can choose pop-up and audio alerts for each column, but I couldn't get the pop-ups to work. The audio alerts, unfortunately, worked just fine. The new version adds support for support growl, so you can always use that notification system instead.
There's also a lot of smaller UI changes. The compose window now appears as an overlay on top of the columns, all external content, including images, launches in an external browser, and so on. Overall, I think the average person will enjoy the small footprint of the app, but power users will miss the extra features. The nice part about missing features, though, is that they can always be added in a future update. You can download Tweetdeck from the Mac App Store for free. Check it out and let us know what you think.