I'm having the same problem as @fidosmarket (using WP 3.0 and WP-EC 6.6.2), where the mouseover hover tooltip is no longer showing up on the sidebar calendar. It's not urgent, as the details do display if the date is clicked upon, but it would be nice to have it back! The 6.6.2 update / patch has been awesome at solving everything else, so many thanks for that! :-)
@LocalVibe - I saw that there's a solution to the multiple events problem on the Events Calendar website. Hope that helps you.