First things first, I've discovered this app about 4 hours ago (~11pm) and I've found myself trapped toying with it, customizing, tweaking and what not. I absolutely love this "little" software you guys have put toghether and, along with "Launchy" and "WinSplit Revolution" it has made my life a lot easier already (or at least I think it will
Anyway, before finding this progam of yours I soared the interwebs trying to find any sort of "virtual screen/monitor video driver emulator", without any luck (this of course is due to my lack of funds for acquiring a second monitor and yet wanting the benefits that would come with one, trying to split the screen into different rendering ports, or something along those lines). I would use such a feature for coding and/or gaming mostly. I believe several users of yours have bumped into your app just like myself trying to find an implmentation of such a feature, and while I have seen many programs that claim to do this, they all fake the functionality simply by forcing a re-arrangement of windows, wich is useless if you want to run several applications in full-screen, each on their own monitor.
Surprisingly enough, even thought your app doesn't claim to have nor has such a feature, it's "Full-screen preview" mode comes astonishingly close, all you'd have to do is "simply" make the desktops interactive (rather than the "limited" functionality of dragging/closing windows and zooming on desktops).
I know it'd be quite possibly a pain in the ass to implement, and I love what you have done so far, but hell, if you are wondering what your userbase wants for future releases, I think this is it!