Here's a list of the most noteworthy things in the RAP 3.0 M5 milestone build which is available for download since February 06, 2015.
Several clipping methods have been implemented:
GC.setClipping( Path )
GC.setClipping( Rectangle )
GC.setClipping( int, int, int, int )
The implementation utilizes the native HTML canvas clipping capabilities. Once a region is clipped, all future drawing operations will be limited to the clipped region.
This list shows all bugs that have been fixed for this milestone build.
The above features are just the ones that are new since the last milestone build. Summaries for earlier builds: