Hi,
I have used GR3, GR2, and GR2AE since 2008. The $250 is a steal for its volume explorer 3D rendering. I know there are other programs that do this function now a days (Baron comes to mind), but be prepared to lay out some serious cash (and most likely a monthly/annual sub) for it. It does not do rainfall rate in 3D. It does do the following in 3D volumetric mode:
Base Reflectivity, Base Velocity, Storm Relative Velocity, Spectrum Width and Rotation in both Lit Volume and Isosurface.
I have not ever had an issue with support from Mike G. or by other members on the GR Owners Forum. There are several professional meteorologists and EM's on the board that use these products everyday in their work, and will respond to questions asked by others.
One thing not readily discussed regarding GR2AE vs. GR3 is the data size of the radar scans. Unless something has changed, the GR2AE scans are about 10 times the size of the GR3 scans that are downloaded to the programs. This is because of GR3 being fully processed vs. GR2AE, which is the raw non-processed data directly from the radar. One needs to have a reasonably decent internet connection (I have a 3Mb connection, which is barely adequate, IMHO) for GR2AE. Also, you can set how often you want the program to scan for new radar data (mine is set to 30 seconds), something you cannot do in GR3.
Hope this helps,
John