I was looking for easy to use Calendar with features such as adding from the frontend as well as the backend, displaying a "Upcoming Events" module and theme support, and I stumbled across JCal Pro. The installation and use of this component is easy, its well laid out and I have no complaints about design. It's well worth your time to try it out at least.
What I was impressed with is the support on their Forum. I was logged in at 1 AM EST and someone (van) happen to be there who helped me nick the problem before I started loosing it. Turns out the problem was with my TinyMCE and not with JCal, so that's a bonus in my opinion.
Give it a shot, you will like it.