FB has a big disadvantage in finding information. FB Groups are not visible in Google Searchresults, so your "forum" on FB will slowly die as nobody finds the information without being a member in the FB group.
This is an absolute no-go for me.
Furthermore, as far as I have seen (I am not on FB myself), the "topics and posts" are not sorted and are very confusing.
It is not possible to have structured discussions.
Yes, we have added a LOT of features to our forums, we have listened to our members needs. Most of the features added are custom programmed.
We have mainly tried to make it easier for everyone to use the forums, created "shortcuts" and made it as easy as possbile to upload photos for example. My community absolutely thrives based on photos.
As of today we have 105K members and 1.2 million posts.
2.1 million page views(?) and 200K unique visitors every month.