I saw the Persona app on the TUAW site and had it give it a try. Persona allows you to easily create avatars on your iPhone. The app worked well besides a few crashing but that could have been the iPhone OS, therefor I recommend saving your avatar as you go. One note is that I would thought they would have added an easier way to share your persona avatar socially. As of right now you can add it to your photo library on the iPhone but I think it would nice If they would add an upload to gallery or a share on Facebook / Twitter feature.
Below are some screenshots from the app and my “Wayne Sutton” persona.