The platform is stable and has the necessary features to replace forum.osm.org. It can be used for everyday discussion of OSM topics and you’re welcome to do so. So yes, it is launched. We’re still working on improving it further, but that shouldn’t stop anyone from using it.
I realize that it’s in a bit of an awkward state because the migration effort is taking longer than intended. Expect us to do another larger round of promotion of the new platform as a whole after that effort is complete.
Individual communities are welcome to request the categories they need, start promoting the new space, and encouraging their members to move over here. (But if some communities wish to wait for the migration, that’s ok, too.)