TweetDeck for iPhone does what I thought was practically impossible: perfectly replicates the powerful column experience of the desktop TweetDeck on the iPhone, and in a surprisingly usable and snappy way.

In a way, performance is actually the most impressive thing about it. Running 4-5 columns, the app responds instantly as you fluidly move from column to column, from tweet to profiles, from account to account. It's running all of these columns simultaneously while constantly pulling updates and alerting you to them—in the form of little popups telling you how many bleep bloops are waiting for you to read them. Around six columns, a hint of slowness starts to creep in, but it's not killer. The only other performance ding is that we had 2 crashes in 30 minutes.

The reason the UI works so well is what it translates the column interface from TweetDeck into a windowed one—they look and work exactly the same as Mobile Safari's multiple windows (faux tabs, or cards, a la Palm Pre, if you're so inclined). You can swipe from column to column or use gratuitous little arrows when it's in full screen, or pop back out to the window view to flick from mentions to a running search instantly. It's really easy to add new columns too—just press the dead-center "add column" to tack-on a running search or to create a new group. You can set how often new columns refresh, and how they're ordered.

For all of the excellent work in nailing the core ideas, there are a few little annoyances—the pointless arrows for moving to a different column, two different buttons to pop into window view, the constant sounds that respond to almost everything you do (thankfully, they can be turned off). You can turn off update pop-ups as well—they appear in at least two different ways, in a notifier box with a badge showing how many updates you have to check out, and as literal pop-ups. The latter seem like overkill, since the notifier box already neatly balances keeping you aware without bothering you.

It's not as elegant as Tweetie, but it's designed to do something different—TweetDeck's arguably now the most powerful iPhone Twitter app in terms of the amount of information it's able to pull in and organize and make instantly accessible. It syncs to the desktop version of TweetDeck, which makes it even stronger in that regard. It's free, and as the most exciting iPhone Twitter app since Tweetie, definitely worth checking out. [iTunes]