TurnKey WordPress features a small footprint, automatic security updates, SSL support and a Web administration interface.
In a nutshell, setting up WordPress as a virtual appliance on your local computer is easier than installing it the old fashioned way, especially if you're running Windows. Many of our users use appliances for testing and development purposes, but virtualization platforms (e.g., VMWare) are now powerful enough that they are being used for production, so it's also useful for that kind of scenario.
BTW, if you want to install a production server on dedicated physical server (e.g., for an Intranet blog), this is an easy way to do that too.
Long story short, we're interested in feedback from the WordPress community, especially if you have any ideas for improvements. One of the things we're exploring is which plugins to bundle with the next version of the appliance.