I've developed a handful of sites using Joomla, but they have been relatively small, low-traffic sites and I was the only publisher. Someone at a larger company saw one of the sites and asked me to develop a site for them. I could do what they need in Joomla but I'm concerned about stability and security (they want to give publishing rights to a number of employees). Are there other CMS systems out there which would be better for a high-traffic site with multiple (and probably not experienced) publishers? It doesn't necessarily have to be open source but it does have to be easy for the publishers to use. And it would be great if the learning curve weren't too steep for a guy who has only used Joomla. Any thoughts?