I just installed the beta today - thanks for the invite! The sign-in and initial sync worked fine, but I'm having trouble downloading anything. This may be similar to @volcanicglass's issue? The circle "loading" icon spins to about the 11 o'clock position, no matter the file size, and then stays there. I tried again and it added the file to the sync list, but the sync never finishes. Permissions were granted OK on first download request.
I've just uninstalled and re-installed and I get the same problem. I'm running Android 7.0. It almost looks like it's waiting to sync one more fire than requested. If I cancel all syncs and try to download a file I get a "Sync 2 files with xx kb" message but when I accept, I still see "Syncing files. 1 remaining".
Otherwise the basics looks good - though I don't like the "one page at a time" scrolling - I'm used to having free scroll. Indeed once articles have been loaded once they can be freely scrolled.