I've been using this for about 6 months now, on a professional education and networking site, and am very pleased so far. There are limitations, and it's difficult to modify for custom needs. On the other hand, it was simple to integrate and manages several types of systems well: membership registration, renewals, payments, event promotion, event ticketing (with member-specific pricing), an event calendar, and email system to members and event registrants all in one. Rather than having these all be independent systems, it's all integrated. That means, though, that those systems may not be as fully developed as stand-alone systems, but the ability to have them all interoperate is a real boost. I hope they'll work on expanding features (beefing up the email system to include templated emails to members, other than the automated emails which are templated, for example). And it's also a bit odd that they use G+ for support, which means asking questions and reporting issues is public rather than private. But they do respond quickly and will take issues private if needed. And yes, it is a plugin that requires payment for groups of more than 50 members, or if you want to connect it to a payment processor. But it's an affordable option for many clubs/organizations, and can help even novice WP builders get something workable and polished up at a negligible cost.