I was reading an article the other day on Grant Skinner’s blog about styles of writing code. me and Grant like to cuddle, who’d of thunk it?
I prefer same line formatting for many of the reasons listed. I would recommend finding a style that works for you and sticking with it. Having your code all over the page makes it difficult to understand what you are looking at.
Flash > Preferences, in the Actionscript category allows you to set the auto format button to follow one style or another. Be sure to set these options and use the Auto format Button often!