I was a long time user of Twhirl as my twitter client, but a while back I switched to Tweetdeck, and today according to my Tweetstats, Tweetdeck caught up to Twhirl as my most used client for updating Twitter. I hope you enjoyed this completely useless personal Twitter fact!
I also prefer tweetdeck. I like the functions and the possibility to see everything very organized in one application. Rightly won!