Very nice tool.
I don't know if was mentioned before, but sometimes water areas do not have imagery in Bing (and sometimes in Google either) and the resulting images are shown in white in those areas. One should have the possibility of editing those images applying alpha layers and saving them after editing, all before the geoconversion process takes place.
Yep. Two points on that:
There's the option to select which tasks you want to run. If you want to clean up images manually just don't run the Geoconvert task the first time.
I'm working on something that detects when I get a placeholder image (or no image) for a water area, and then making that area transparent in the PNG I create.
This reduces the necessity for manual editing. (Manual editing would make the graduation of coastline smoother, but the automatically generated images will have transparency out of the box).