I recently moved the Open Data Kit community from Google Groups to Discourse. The process was painful (3.3K users, 25K messages), but as you can see at https://forum.opendatakit.org, it was totally worth it!
I got a lot of help from the Discourse community along the way, so I’d like to pay that favor forward and help a couple of communities with their migration.
If you’d like help moving your community from Google Groups to Discourse, please send me a personal message!