I've been using Event Espresso for almost two years now. It is the best event management and registration tool I have found...and I've tried many that were much much more expensive.
I love the fact that users don't have to leave my website to register and everything I need is right in the WordPress CMS. I have monthly events and I have never had one complaint or question about registering.
Thanks for the great plugin. I wouldn't dream of using anything else for my events.