Netbeans 6,8 beta here with the latest Appengine (appengine-java-sdk-1.2.6) GWT (gwt-windows-1.7.1).
Running the project is not a problem.
Debugging is different story. It got stuck at
[OUTPUT: Google App Engine]
runserver-debug:
[java] Listening for transport dt_socket at address: 8765
The port is correct. Silly work around is to debug sample guestbook project (which is not GWT). Stop it after it open the page (and the app engine server is already running in debug mode). And then debug the GWT project. This works.
Bug
Open
Major
Unable to debug GWT, suspected appengine (debug mode) server is not started
This problem can be resolved by changing the ant-deploy runserver-debug target to not suspend the server on start.
<arg value="--jvm_flag=-Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=${appengine.debug.port}"/>
<arg value="--jvm_flag=-Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=${appengine.debug.port}"/>