I have been using CodeTek VirtualDesktop since it appeared and it got better with every update. The tech-support is prompt and efficient, even during the trasition period to Tiger when there were a few rough spots.
I was afraid Apple's Entourage will make VT obsolete, but I find that I never need Entourage.
With 6 desktops (tied to specific applications, like Browser, Media, Graphics, Mail, Text, X11), my screen is always uncluttered. In fact, CodeTek's VT is much more elgant than the various virtual Desktops we are familiar with from
Unix (Gnome, CDE, KDE, etc.). It has never crashed or locked up on me since version 3.1.

Thanks to Bill Goldstein and his team at CodeTek Studios, Inc for a super-app!