It's a great alternative to using a third-party, like Eventbrite. You host and manage events from within Wordpress, so it's possible to build out a more robust presence for your event, including supporting content, downloads, etc. Additionally, there's a lot of flexibility, in terms of email templates, payment options, payment integration gateways, question types, etc. Being able to invoice and pay offline, as an option, was fantastic. The product is being actively developed, with new versions and plugins being regularly released. I've also found the support forums to be pretty responsive.