I don't consider this a bug, but I also wasn't sure if this qualifies as an enhancement request, but here goes...
On my Vista desktop at home, I can right-click on a JPG image file and choose "Open with..." and then "Paint.net". However, if I highlight multiple files, there is no "Open with..." option anymore. Only "Open" and "Edit", which opens in the photo or picture manager app. Is there a known way to get my computer to support opening with Paint.net with multiple selected files on Vista?