I've been using Tweetdeck for the desktop for a while and enjoy it. On the iPhone i've been using Twitterfon Pro and love it. Well Tweetdeck came out with their iPhone version today and I wanted to check it out. I thought I'd share a quick review and comparison. This is just my opinion so use it as you will.
First off Tweekdeck for iPhone 1.0 uses a unique interface. It uses the panels just like the desktop app, and you can swipe between panels. Take a look at the main screen here:

as you can see it shows the total number of new tweet updates in red on the bottom left. You can see the different columns and swipe between them. to view a column just click on it. then it comes up like this:

from here you can scroll up and down, etc... the arrow in the bottom right will take you to the next column. to go back to zoom out column view you click the columns button in the middle on the bottom.
Here's one of the things I prefer Twitterfon on. To view a link in a tweet on twitterfon you can click on the link directly in the tweet. On Tweetdeck you have to click on the tweet to pull up the details, then you can click on links from the tweet and do your replying, retweetind, DM, etc..

A couple of interesting features are the ability to email the tweet (shown above) adding more columns to support search terms (like the desktop app), the ability to sync tweetdeck iphone with the desktop app (you must signup for a tweetdeck account to sync), you can choose between twitpic and yfrog, and the ability to add multiple twitter accounts (twitterfon pro supports multiple accounts too). When you start a new tweet the input screen looks like this:

Now let's take a look at the Twitterfon Pro screens and compare.

To me the interface is a little more clean in Twitterfon. It shows the number of new tweets, mentions, and DM's. It's easy to distinguish new tweets and mentions directly in the list. the great feature in Twitterfon is that it will auto scroll you down to where the newest tweets start. It doesn't just leave you at the top and make you scroll through them backwards. Also notice how links are easily identified in the main list and you can click these links directly from here. you don't have to click on the tweet first. You can also click on the twitter's name to go directly to their profile. You can also make a tweet a favorite from this screen by clicking the star on the right of the tweet. Once you click on the tweet, you get this screen:

Once again the buttons are very distinguishable and you can do everything from here. reply, DM, retweet, favorite. hit the users timeline and their profile. Below is the search screen:

As you can see here you can locate local tweets. basically all tweets around you based on the radius you choose. I chose 5 miles. Click in the search field and search for anything. if you leave the search term in. it will constantly update to find new tweets with your search term. Even when you quit and come back in it will update with new search tweets.
Here's Twitterfon's input screen. as you can see it's very similar to Tweetdecks, but it also has a trash button to delete the tweet your writing and start over.

But the coolest feature is the landscape keyboard. turn it sideways and get this:

Twitterfon also has 4 themes to choose from. Silver (shown in the shots above) Twitterfon, Plain, and Black. Shown below:



Another really cool feature is Twitterfon lets you install a bookmark into Safari Mobile to tweet any page/link. It saves it as a bookmark. then when you're surfing you can be on the page you want to tweet. choose the twitterfon bookmark from your bookmarks and it will send the page link to twitterfon and open up a new tweet. Very cool!
As you can see from the screen grabs, they are very similar but overall I still give the nod to Twitterfon. The interface is better and it's easy to see and select all the options you need to tweet.
Tweetdeck is pretty good, but I think it still needs some work, but it's 1.0, so i'm sure it will get better. Tweetdeck is also FREE! And Twitterfon Pro is $4.99, although their is a free version (it adds a small ad to very top, doesn't support multiple account, and doesn't have the landscape keyboard) Like I said before this is personal preference, but hopefully you can use this info to make a better decision.
Have any questions about these 2 or something i missed? Leave a comment. Thanks!