I have version 3.5.0.83 from the Good e-Reader site
here and it works for me on my Vox. The version I tried a little while before did crash, but I'm not sure what version number it was. I got both from the Good e-Reader site - the same link actually - so they do update their versions of the app.
Installing this latest version of the app did give me access to Amazon's Personal Document Service. I noticed after installing it that Amazon gave me a Kindle email. I didn't have that before.