Just have to say I have had great luck with this plug-in... When I have had questions, the developer has been quick to respond and is seems to be open to future feature requests.
We used this on non-profit that so far has had 300 signups in under 24 hours and we haven't had any issues.
I would like to see a little more options on the security side - I believe you need to be an admin to download the CSV but it would be nice to allow the Editor level security to do so as well. Would also like to be able to have a system where you can send out an email update if they have been accepted. I think the latest changes allow you to customize your own way of doing that - I just haven't had time to play with it.
Thanks for all your hard work!