Your homepage should definitely mention that Mac is the only supported client. Take a look at the OS statistics from the hits on your site - my guess is that most are not Mac.
Mac only really is a bummer. I realize that there's a large and vocal crowd of developers doing that, but there's also a big Windows/.NET crowd you could easily be targeting with this. Seeing this on Windows would be great, if you use the open source VirtualBox you can easily make cross platform images.
As others said, it would be good if you indicated only OS X support. I just assumed from the screencast that at least any *nix system would work. Surely making a Linux client isn't far off, though, right?
We only support Mac os x at the moment as a client, and Linux as the dev environment.
That said, we will be looking to expand at some point. At this stage, we want to make sure we nail down the correct way of solving this problem.