Windows only 
With Windows XP there were several PowerToys that added awesome features to the operating system, such as virtual desktops. Unfortunately with the release of Vista many of those free applications no longer worked, and users were left trying to find alternatives.
Sysinternals, who is part of Microsoft, took it upon themselves to develop a virtual desktop application that is compatible with Windows Vista. It’s not quite as fancy as the Vista Virtual Desktop application we reviewed last year, but the original Microsoft PowerToy wasn’t exactly busting at the seams with eye-popping features either.
At this point all you can do with the program is see a preview of up to four virtual desktops by clicking on the System Tray icon. You can also customize the keyboard shortcut used to switch between each desktop, but other than that there isn’t much else it’s capable of. The one feature I am really looking forward to is dragging and dropping windows from one desktop to another, but there’s no mention as to whether they intend to add something like that.
Judging by all of the hard work that Sysinternals has put into Process Explorer (review) this virtual desktop manager will probably get the attention it deserves.
VirtuaWin runs just fine on Vista. Many desktops can be run and stuff moved between them. Not drag and drop, but just a couple of mouse clicks.
Well, I’ve just tested that.
It is far behind Desktop manager
of Power toys for XP. Major drawbacks
(in my opinion):
1) Impossibility to normally close the prog.
This means, in particular, that Hot keys registered for
the prog, remain occupied after the prog is forcibly killed.
So I associated to it the hot keys CTR+ALT+SHIFT+WIN+F#,
before killing it (this combination is not used by any other prog, anyway, so no conflicts will arise).
2) No possibility to have different backgrounds for different desktops.
3) Impossibility to make some windows sticky.
It’s definitely not a full-featured virtual desktop application as you guys have pointed out, but for a first release it’s not all that bad. I expect that over time they’ll add a few features here and there to make it work better.
Not drag & drop? Then how do you move windows from 1 desktop to another?