Ranked in these QuestionsQuestion Ranking
Has a free trial version and a cheap full version.
Pro Scripting support
Can be used to generate models, import stuff, animate, etc.
Pro Interoperates with 2D paint programs
Pro Supports both "per voxel" drawing and smooth "sculpting"
Pro Uses 32-bit color with real volumetric transparency
Pro Easy to use
Pro Supports multiple voxel formats
Pro Can export traditional 3D models
Con The web site's domain is no longer available
Using the WayBackMachine to get the site's contact email address, I attempted to contact the developer to find out what the story is. There has been no response. The WayBackMachine's last archive date for the site was 11Jan2016. Their cached version of the paint3D.net's forum does not have any post explaining what happened.