Some users have had some trouble using the Pack Installer with some firewalls. I'm not sure exactly what the solution is yet, but it seems to only affect the list of tools being downloaded, not the actual Power Toys themselves. If you have a problem and
refreshing the list doesn't fix it, you can download the PackFeedBeta.xml file that is attached to the Wiki page and drop it in the same folder as the Pack Installer executable. This should get you up and running.