GWT 1.7 is a minor update that adds better support for Internet Explorer 8, Firefox 3.5, and Safari 4. Each of these new browser versions introduced at least one change that negatively impacted compiled GWT modules, so we recommend that you do update to GWT 1.7 and recompile your existing applications to ensure that they work well with the latest versions of browsers. No source code changes on your part should be required.
Normally, a minor update such as this would have been named 1.6.5 (the previous latest version of GWT was 1.6.4), but we did add the value "ie8" to the "user.agent" deferred binding property, which could impact projects using custom deferred binding rules that are sensitive to that property. Thus, we went with GWT 1.7 rather than GWT 1.6.5, to indicate that you may need to pay attention to that change. Details are in the release notes.
In every other respect, this is just a bugfix release, so in the vast majority of cases, the update-recompile process should be nearly effortless.