That lucky man Kevin Rose got access to try out the beta of TweetDeck for iPhone early. From his comments, it sounds good, the feature list (below) backs that up. So look out Tweetie, looks like many people will be leaving you for TweetDeck.
Personally I use TweetDeck as my desktop twitter client of choice, so to have a seemless desktop / mobile experience is definitely advantageous.
The app has been submitted and available in the App Store for free, just as soon as Apple approves it. Hurry up Apple !!
Tweet directly from your iPhone or iPod Touch.
Manage multiple Twitter accounts.
View notifications for new tweets received.
Use columns to create your personal dashboard.
Simply sync to set-up
Continuously updates between your desktop and iPhone.
Create Groups to easily follow all your friends.
Follow topics in real-time with saved searches.
Reply to tweets and send direct messages.
Easily re-tweet messages.
Share photos with Twitpic and YFrog.
Shorten links with your favourite URL shortener.
Follow and un-follow people.
Shake your iPhone to refresh columns.
More @ TweetDeck + KevinRose.com via Gizmodo