I have quite a bit of experience using web-based Content Management Systems. I have used and developed extensively for Mambo, Drupal, and most recently Wordpress. I have tried out a handful of others, but I cannot say I have an in-depth view of them. As far as popularity goes Mambo/Joomla, Drupal and Wordpress probably account for a significant number of CMS/blogging platforms on the net (at present). So, take this from my user-developer experience, and usually from the perspective of something I call developer-usability. Developer usability is an important factor in choosing a tool to manage your content online, and hopefully developer usability and user usability are high goals on the platform's agenda, In fact, usability is a not-for-negotiation goal/feature.
Because it is fun to google yourself I googled new media, and found that we currently sitting on page three (at around position 22) on the results page. If you use the South African Google we come up fourth, and if you constrain it to only South African pages then we are number 2. I also tried a search for citizen journalism and our tags section comes up as second. It is a bit arb, but it means we do have incoming links from Google for relevant stuff.