it's more like spaces, I think... I don't know waht Virtue is. different desktops for different workflows at the click of a mouse with effects.
Virtue Desktops grew out of Desktop Manager. I use Virtue on both my Macs. It has a lot more features than DM (which has been dead for awhile), since it was maintained until last month when the developer announced he was leaving it to work on other things, since Spaces would come along in a few months anyway.