Okay, yeah there's a couple of minor bugs, which you may or may not have seen yet. However this does actually work and runs quickly most of the time, even on my iBook 500.
Finder windows seem to stay open in the same place regardless of which desktop you're on, and will jump to the front of their own accord.
I'd like it if you had an option to lock the resize sliders in the preferences, so that you don't have to keep fiddling to get the proportions right. Perhaps just make it one large slider.
Also in preferences, you have a transparency slider which, when it is slid all the way to the right, means "no transperancy at all" and all the way to the left means "completely transparent." This seems a little back-to-front to me.
Also, you could make the preferences dialogues a fair bit smaller.
I hope you are coding this with the option of adding more desktops at a later time. Having one virtual desktop seems a little weak. Also, it would be nice if this could be a dockling, with the alternate desktop appearing as an icon in the dock.
As far as I can see, it automatically hides whatever isn't on the current dektop, and shows what is on, each time you switch. (I have used tinkertool to shade icons of hidden apps in the dock). In the meanwhile, it is snatching an image of your desktop to go in the preview window. All up, it is an efficient and well thought-out design. A little more sense on the set-up and installation is the important thing.
And it is, of course, counter-intuitive to have to pick desktop images again. Why not just use whatever the user is currently using as their desktop? And what happens if someone DOESN'T choose a desktop image in the setup dialogues? (I read the warning that you MUST choose a desktop image for both)
Also, taking a snapshot will cause Finder to restart itself ...