Joomla is probably the second most popular content management system on the web today. It's what I worked with before I found out about WordPress. It actually has more capabilities for businesses than WordPress does but WordPress has grown in such a way that it is now a direct competitor.
I like to work with both WordPress and Joomla because there are so well supported by other Developers. I've been doing so since they were born. While I'm not a 10 year old coder and don't learn as fast as they do I have learned a lot about both cms's and I'm prepared to help others anyway they need.