>why would I use this over VNC when this costs $299 US and VNC is free?

Support. The VNC web site looks like it hasn't been touched in a year. There is nothing there about OSX or Windows ME, for example. AT&T Labs has been largely gutted, so long-term support seems unlikely.

This is all sad, of course, because VNC looks great, and open source for something like this is a Good Thing.