For as much as I think TweetDeck is an excellent client, I would still far prefer to run a Mac-native client rather than an Adobe AIR one (and please note that I felt the same way when I was on Windows primarily — this is not an Apple vs. Adobe hit). There are some great native Mac clients out there, but I’ve yet to find one running User Streams for real-time Tweets, and my expectations now outpace the periodic refresh that most clients offer. (It’s why I have had a very love-hate relationship with Tweetie for Mac.) Are you running one? Did you write one? I’d love to hear about it.