The latest beta is ready for testing. There's one thing in particular that I could really use help with. This beta includes multiple versions of Harlowe and SugarCube so that you can upgrade to the 2.x release series of both when you're ready-- however, it's really important that when 2.1.0 is released to the public, it gracefully keeps stories with the right version.
So, if you have time, please download it
and let me know if anything unexpected happens with your existing stories. I've tested it myself, but I'd like to be absolutely sure it works as expected before the release.