Regarding GWT 2.4, Use Firefox when debugging GWT, it alot more faster then using chrome.
And if you'll using only firefox, consider putting this line in your project.gwt.xml file
Also, If you're using eclipse, then add the following under arguments -> VM arguments:
-Xmx512m -XX:MaxPermSize=1024m -XX:PermSize=1024m
You can divide your server and client, and use the following under arguments -> Program arguments:
-codeServerPort 9997 -startupUrl http://yourserver/project -noserver
Also, to prevent refreshing your server on each change, use JRebel
http://zeroturnaround.com/blog/how-to-rock-out-with-jrebel-and-google-web-toolkit-gwt/
And here's a live demo
http://www.youtube.com/watch?feature=player_embedded&v=4JGGFCzspaY
