Some users are reporting the app crashing on Windows 8 devices immediately when launching. This should fixed in Release 13, which is currently in Windows Store Certification. I apologize for the inconvenience. Please check back here for updates on when the release will be available for download.
UPDATE (05/09/2014 14:26 MT): Release 13 is now available in the Windows Store, and should resolve this issue. Please advise if any further problems persist with this release. Thank you!