After seeing some of the benefits of GWT, my partner and I decided that it would be a good front end for the web app we hope to build. A main part of this web app will be content management. We were hoping to use a CMS framework and put GWT on the front end, but all the open source CMS systems we find seem to be very tied to their front end.
Does anybody know of a CMS that would work well with GWT?
No, but I can tell you that using a Java based CMS will make your life much much easier. GWT lives on RPC calls, and while translation / JSON overlays are possible, you're much better off with a Java backend.
You mind find this difficult, though, because when you want to use GWT you're doing a massive amount of work on the front end, leaving the backend mostly data processing and storage. Since very few CMSs are designed to do nothing more than processing and storage, you might be better off building your own.
That said, you might find it very easy if you're open to using App Engine. The GWT + App Engine stack works really well, now has a great Eclipse plugin dedicated to it, and is free to get started with.
I think it all depends on how much integration you want, specifically, what you want to do with GWT. We have successfully integrated GWT with Documentum + Java on the back end.
With that said, our integration is fairly light. The site is largely a content oriented website, but we use GWT to:
Unfortunately, since this is something I do for a client, I cannot specifically mention the site by name in public, but if you're interested, I can share some details with you via e-mail.
Try the Nuxeo CMS/EMS, which is implemented in Java. Search google for "nuxeo", and also search for "nuxeo gwt" for a variety of tutorials on integrating GWT with Nuxeo.