"In doing some mobile apps, I’ve noticed that for the scope of the project, sometimes 3 weeks or less, the verbose language actually gets in the way. So, I was looking for a higher level language, and Lua in Corona SEEMS to fit the bill, but I’m still learning. I liked how I could save a file in TextMate and and it would just refresh the iPhone/Android emulator. HOTNESS! Uber fast compared to mxmlc and “Building…” in Flash Builder, even when using pure AS3. The interpreted nature of Lua helps speed that up (I guess)."

http://jessewarden.com/2011/01/lua-for-actionscript-developers.html

This is a great article with lots of examples showing Lua side by side with ActionScript 3.