I finally got around to paying the extension developer fee, and become a “real” extension developer. This means that for the new versions of ViihdeHelper, you no longer need to mess around with the “Developer mode” and unzipping files etc. You just have search for ViihdeHelper on the Chrome Web Store, and add it to Chrome from there! Alternatively use this link: http://bit.ly/ViihdeHelper
The other information on my Elisa Viihde page about the extension still holds (configuring via Options link, VLCLauncher for open in VLC functionality etc).