It's a little unfair to compare RISC OS browsers with the Windows Desktop, as if this is anything other than comparing them with IE. Sure, there are holes in RISC OS browser capabilities, but that's a different issue, really (wouldn't you say?).
I agree there's nothing wrong with having additional flexibility on the desktop, but it has to be said that the Windows Active Desktop is a pretty bad implementation in my opinion. E.g. it annoyingly changes the behaviour of file icons and the context menu. You can do some clever stuff with it, but really it's no different to having a separate layer of windows behind the normal one. In my opinion it's a cludge to get around the fact that windows jump to the front all over the place and there are no virtual desktops.
One of the reasons I like this article is that (as well as providing a neat idea) it highlights the way RISC OS works differently from most desktops on other platforms. That is, it's not just a virtual folder and is controllable using scripts.