Switched from Eclipse to IntelliJ for AppEngine development
Eclipse has been my tool of choice for AppEngine development because of the great plugin supplied by Google. I have been using IntelliJ for all other Java, Scala, and Clojure development so I decided it would be nice to switch AppEngine development to IntelliJ 9.x also. If you decide to do this also, after a few false starts, I now have a recipe that works for me:
Install the latest Java SDK for AppEngine and set a symbolic link to it so it is easy to swap in newer versions as they are released.
Don't import the eclipse project. Instead, I had better results creating new empty AppEngine projects and copying in my src directory and the contents of the old war directory to the web directory.
Create an AppEngine facet, entering the symbolic link to your Java AppEngine SDK directory.
Create an artifact of type Web App Exploded.