It's a slightly different programming model (using proxy objects instead of real the actual data model objects), but I would recommend using the official GWT requestfactory as a replacement: https://developers.google.com/web-toolkit/doc/latest/DevGuideRequestFactory
We've found it to be a much better programming model as it doesn't force you to keep your model classes clear of any server side code. I believe it also has a number of performance benefits as it automatically manages changes as delta's rather than reserialising the entire object.