I am having the same problem. I’ll try to be less ranty about it, but it’s definitely frustrating.
I am importing a forum from a wordpress 4.1/bbPress 2.5.4 install on an old site to a wordpress 4.1/bbPress 2.5.4 on a new site. There’s no way to do this from the Import Forum screen, so I also have done this via the standard WordPress Export/Import tool as suggested.
In my case, content shows up on the back end, but not on the front end. Also, accessing the Replies page on the back end results in a segmentation fault on the server. Taking these steps with no plugins and default theme has the same results.
Like the original poster here, I would love to find what is the correct import procedure to just move a bbPress install from one site to another.
