I am still using the original Air based TweetDeck. I upgraded to a new computer just after the product was bought out by Twitter and got stuck with the new TweetDeck app, which is about as close to a tragedy you can get in comparision.
I tried a BUNCH of other clients - Sobees and Seesmic came close to doing the job - but none of them did as good a job as Air TweetDeck. I can't seem to find the Air installation program for the last Air release of TweetDeck, so when at home, I'm now stuck to using two computers at the same time, if I want to Tweet - my laptop still has the old TweetDeck installed.
I'm, no programmer, but I'd certainly support someone's effort to rebuild the original TweetDeck or to build a client with the same look and feel. If you are familiar with the Air version, compare it to Sobees and Seesmic to see how you can get close and then totally fark it up with inscrutible interface design.
If fact, that's the major problem with almost all Twitter clients out there. They are made by people who haven't got an effing clue about interface design. I think they saw how perfect TweetDeck was and decided the only way they could compete was with a different look and feel.
They were horribly wrong.
Twitter is the only social site for which I use an app. I'm on Google+ regularly, but their web interface is quite good. I also have a Facebook account, but only use that to stay in touch with friends who only use Facebook. When the next ice age comes, I will ensure they are sent to the leading edge of the glacier to stand there and hold it back - neanderthals that they are.
I use several others, but that might take the track of this discussion too far afield.