I'm using this on a site that we are running and it's working really nicely.
We only use it for comment integration, not really interested in SSO, as we don't have multiple WP authors who would also be using the forum.
There are a few things that I don't quite get though, and one of the must urgent and strange is the difference in the number of comments on WP and in Flarum. I'm not sure if it's something with my implementation (but I'm fairly sure not) or a bug, or by design for some reason, but seems wrong whichever case it is.
See attached images below for an example post - the number shows up correctly in WP, but is always one less than the actual comment count in Flarum.
In Flarum:

In WordPress:
