Just for general information, there is progress being made in the area of GWT and PUSH/Comet components. As Vaadin ins pure java, only a pure java solution would make sense.
Here are two projects that integrating atmosphere with GWT:
- atmosphere:
https://atmosphere.dev.java.net/
- gwt-atmosphere:
http://code.google.com/p/gwt-atmosphere/
- gwt-comet:
http://code.google.com/p/gwt-comet/
, story
http://blog.jabbah.co.cc/2010/03/integrate-atmosphere-with-gwt-comet.html
Once servlet 3.0 and later HTML5 sockets create an expectation from users, there is no more going back.
I up the vote for vaadin to integrate atmosphere.