One of the great things about Debian is the vast number of packages available for easy installation. No matter what you're looking for, chances are you're just a simple apt-get install away. Searching for packages in Debian (or Ubuntu) from the command line has always been easy with apt-cache search. What more could you want? A sign of a great company is the ability to anticipate needs and although Debian isn't a company per se, I think they've done a great service by launching a new site aimed at gathering screenshots.
Face it, no matter how easy it is to install a package and no matter how fast your internet connection is, sometimes you just loathe to sully your box with an app you may need to just uninstall in a few minutes. If you could just *see* what the application looked like you might even know if it did what you wanted. (Case in point, I'm still not sure if Kate in KDE4 has a tree view!)
I think it's brilliant. The one thing that seems interesting is that you don't have to register to upload a screenshot. Instead each file is reviewed by an admin team. While that may not scale in the long run, it's easily fixed through Open-ID. Rock on folks.