While Whonix utilises Tor, it can offer advantages over a purely Tor-based approach, particularly when it comes to the dangers of applications or browser plug-ins, such as Flash and Java, leaking IP addresses. Because of the sandbox setup, applications running on Whonix-Workstation can at worst only leak the IP addresses of the internal (virtual) network.
Because it's a project that focused on anonymity and privacy, it is hard to get a picture of its user base; however, there have been approximately 14,000 downloads of Whonix-Gateway 0.45 directly from the project's Sourceforge homepage. (This number doesn't reflect those who built the project from source code or downloaded from mirrors.) "This is not a bad number, because the Tor network in total has 500,000 users," Adrelanos says.
As for who is using it, that is, naturally, even harder to know, Adrelanos says: "Use cases have included journalists, admins of hidden services [sites whose address is obfuscated by the Tor network], businesspeople, activists, hackers (however that word is defined and understood), people who want to protect themselves from hackers (or crackers), users who just want to protect their privacy..."
The task list for the project is "endless," Adrelanos says. He plans to improve pretty much every aspect of Whonix, including increasing privacy and making it more resistant to more sophisticated attacks, adding multi-language support (both for the OS itself and the website), improving the documentation, working on an encrypted USB installer, adding an updater for the OS, and working on a graphical gateway.
There's no funding and very few contributors (of the three or so people who started the project, Adrelanos is currently the only active developer), but Adrelanos says progress "will remain steady". (Though he adds "there are no promises about what gets finished and what gets done, and what may never get done...")
He's keen for more contributors to join the project and says it's easy to get involved (Whonix has a page explaining how people can get involved.) Even contributing to the technical side is not that difficult, Adrelanos says. "Whonix mainly consists of application configuration files and Linux shell scripts. No real programming (in C or assembler) is involved yet. I believe developing something like Tor, Firefox, drivers, a compiler etc. is much more difficult than developing Whonix."