The feature that downloads extensions from the Runway website and installs the extensions fails, or, at least, it failed for me.
The problem appears to be that the extensions are doubled-zipped so the installer unzips the package to reveal another zip package. The same extensions can be downloaded, unzipped and the internal zip file installed through the extensions installer.
Not necessarily a bug in Runway unless Runway is supposed to unzip the extension then unzip the unzipped package.
Runway looks really nice. Really like the standalone theme exporter. I'm going to have a good play with this theme.