I like that you're trying to tackle the specific problem of real-time remote collaboration and made a tool to address that - that's great! The difference for me is that I rarely see value in it, compared to just scanning in a quick sketch and then collecting input via IM or email, or even with getting other scanned sketches back in return.

For example, here's a quick sketch by Jason at 37signals to get across the overall layout of their new home page:

http://www.37signals.com/svn/posts/1629-preview-of-the-new-3...