Using the new Konfabulator for Windows since it was released on Monday, I can already say - very cool, useful functionality and a worthy enhancement to the Windows desktop.
For instance, I very much like being able to see at a glance what the weather's like in Amsterdam (or just about any other city; data comes from Weather.com), including forward forecasts, and seeing the time on a nicely-designed analog clock that changes its background colour depending on whether it's a.m. or p.m. Best of all for me is a neat little widget that graphically shows me the signal strength of my wireless network.
Loads of other widgets in the installation - such as post-it notes, a nice little photo display widget, battery meter, etc - and you can download loads more from the Konfabulator website.
Each widget I have loaded takes up less than 10Mb of memory, with no effect at all on system performance that I've noticed. This would present no problem for any reasonably recent PC running Windows XP or 2000.
The functionality aside, I love the way in which the program is designed. You can tell its Macintosh origins: very warm and friendly conversational-style dialogs during the installation, and you interact with widgets so they come and go with very nice and smooth transitions.
For some time, I've been a user of widgets that run under DesktopX from Stardock. That's an excellent application, too (and does a whole more than just let you have widgets on your desktop). But for its simplicity and sheer style, Konfabulator for Windows is a winner.
Now, Konfabulator's not for everyone. What your desktop looks like and how you want to interact with it is a highly subjective experience. For instance, one good friend of mine likes her desktop with all the little Windows folder and program icons neatly lined up in vertical rows on the left of the screen. I hate that myself! I like a gorgeous photo background (from Webshots) with minimal icons. I use ObjectDock (again, from Stardock) which smoothly appears from the top when I move my mouse up there. My friend hates all that, but I love it! So each to his or her own.
Is Konfabulator for Windows worth paying $25 for? Well, as I've already got DesktopX, I'll fully make up my mind on that when the trial period expires.