As a consultant, I've used Higher Logic with several clients. I've completed the organization demographics on behalf of the client for which I've done the most Higher Logic work.
The good: Higher Logic is probably the most complete online community platform I've worked with. Full CMS, elaborate configurations, community automation, reply-by-email, event registration, blogs, forums, member management, volunteer management, and more. Relative to other platforms I've worked with, Higher Logic is among the best at reply-by-email functionality, meaning that a user can participate in forums without having to log into the community. I think their community automation features are far and away the best on the market. Excellent support, and an extremely innovative product team.
The bad: Not much to say here. The out-of-the-box design looks a little dated. Different areas of the admin areas feel a little disjointed. It's a very big tool, and the learning curve can be steep.
Bottom line: You can't go wrong with Higher Logic.