Good product, with some reservations
We've been using Higher Logic for between 3-4 years and I'm generally pretty happy with it. We have a lively community that adds significant value for our members and it has some great reporting capabilities that allow you to get useful and interesting data that would be hard/impossible to pull from most AMS's.
Customer service is generally good--the staff are knowledgeable and are great about things like producing screencasts to walk you through things. Each customer has very different needs, so it's no small feat to be that helpful.
My biggest complaints are that the platform isn't terribly easy for the end users compared to the platforms they're used to (like Facebook, Twitter, etc.) and ease of use doesn't seem to be a priority to them. The other complaint is they seem focused on rolling out new features rather than improving those features that still need refinement. People have been begging them for years to send notificatoins when people get replies to their posts, for instance, but that's never been addressed, and instead they release features it doesn't seem like anyone has asked for.
