I recently had the opportunity to test out an interest bit of software called Fishbowl (www.fishbowlclient.com).
Fishbowl is a Facebook desktop client designed for Windows. User are able to logged on to Facebook and view their Friends updates, photos etc via this neat little application.
While this software looks complete, uniquely this is only concept software simply just showcasing the potential of Windows 7 software development. However, it will not only run on Windows XP and up, it is usable software (see system requirements). According you the official MSDN blog, it has been developed using Microsoft Silverlight and Windows Presentation Foundation, which is similar to the now popular Adobe AIR platform.
Visually, it is very similar to the standard Facebook website. The familiar blue setting and similar layout will help user feel right at home.
Although this software DOES allow you to change its colours, it's nothing to get excited over. The colour selection is as follows; Facebook Blue, Blue, and Dark (or Navy Blue). If you like your blue, this app is for you. Again the general layout and design of Fishbowl is simple, familar while at the same time being quite elegant.
There is a "Mini-Mode" which transforms the standard looking interface into a small and tidy, Windows Gadget-looking thing that can be simply tucked into the corner of your screen and watch the status updates roll in. However this doesn't actually streamline into Windows' actually gadgets.
Photo uploader is simple enough, offering a drag-n-drop facility and allowing you in the same step to create a new photo album or import the photos into a existing album. Works well.
They have stuck with the traditional News Feed for listing status updates, in contrast to the actuall Facebook pages' News and Live Feed pages. I found this easier to deal with.
Problems I did have with this application was that it did NOT have chat support. Surprising as there are plenty of Facebook chat clients available (i.e. Digsby) and has become an essential part of Facebook.
Also, when updating your status, although Facebook has registered you just updated you status, the client failed to refresh your last status update line in the application which does make it confusing whether it worked or not.
Overall, this is a nice simple application and does accomplish 90% of what users do on the Facebook website, but obviously as concept software they haven't included everything.