I installed this forum earlier today and had no problems what so ever installing it. It really was a clean and smooth install and just as easy as installing any other plugin in WordPress.
I had one issue when creating new users, but I watched this video and it walked me right through it: http://www.youtube.com/watch?v=t66BST_kU6g
So far the only thing that keeps Mingle Forum from getting 5 stars is that it's pretty difficult to change the skin. This really has to be a lot easier in my opinion.
But other than that it's really great and easy to use.