I use Working Copy and iCloud sync in Beorg. I have noticed a few syncing issues: after making an edit, the sync progress bar at the top of the interface flashes on and off several times (flashes on/off twice per file, I think?). Making any edits while the sync progress bar is flashing is difficult because the interface interrupts you, and any edits you do manage to make seem to be lost. I've found that I need to wait for the sync status indicator to completely settle down before making another edit.
I use iCloud sync only for the purpose of moving files between beorg and Working Copy. Working Copy supports repositories whose checkouts are in iCloud folders.