This plugin was incredibly easy to install and setup. Both the back-end and front-end interfaces are very easy to figure out, and each event you create is highly customizable. If there is something you need and don't see, just submit a feature request on their website. The plugin itself is very frequently updated, and once you buy it, you keep getting free upgrades.
We had a few problems at first with loading the confirmation page, and some other minor issues, but Tuan was extremely helpful and quick to respond--we'd usually get an answer the same day. He also went in and changed around some code to do a small customization for us.