This is an excellent extension, it provides a great calender for events planned for my non profit martial arts club. The ability to have searches for gradings or meditation makes it very easy for users to plan their lives and activities. The icing on the cake is to be able to assign security access to the people responsible for the events, less work for me :)
The module which shows the next 5 events is good on the frontpage as it helps to show that the club is active for the new visitor, and for our members provides a quick access to up comming events. All this on the free bit, I am sure if we need anymore than the basic facilities we will join up for membership.