I tried it with my very own blog, and it works well. It loads quickly over EDGE, and is easy to navigate with one finger.
But the news doesn't stop there. The good folks at Six Apart also mention that they are hard at work with the iPhone SDK to produce a native iPhone app for Typepad blogging. I used a previous Windows Mobile native client from Typepad, and it worked well so I can only imagine what they will be able to do on the iPhone.
You can check out all the mobile features of Typepad, and sign up to get notified about the iPhone app, here.