Hello Davide,
I've just found your plugin and seems this is great for my needs.
I need a simple RSVP plugin and yours was the most up-to-date available.
I did install it correctly, got a google API key.
Unfortunately, *whenever* i try to edit or create a new event, when I press the "Submit Event" button, it stays forever in there... no reply at all, I have to kill IE8 and restart it. Have you ever seen this before? I'm now going to try on a fresh WP install and will let you know the results.
Ciao,
Rafael.