I became a Twitter convert at this year's TechEd North America. It really was the best way to communicate and send status among friends and colleagues about session information, locations for swag, and "Let's meet outside the TLC" messages.
I tried a lot of Twitter clients for my Windows Mobile device, but by far the best was Twikini by Trinket Software. The application is fast, lightweight, and highly customizable. Even better, it integrates well with other online apps like TwitPic.
Trinket Software released the non-beta version of Twikini this week. If you're a Twitter user, I highly recommend you check it out.