About a year ago I switched from JabRef to Mendeley and fter this unusually long test run I am quite happy with it:

• it keeps my references in a cloud, so I can easily sync refs on my laptop and desktop machines;
  
• I have sorted my references into folders by their topic and by the project;
  
• my colleagues and I have created thematic groups through which we share relevant publications;
  
• I can search for papers at mendeley.com -- comes in handy when I am outside of university's network and do not have access to some journals
  
• I can add papers to Mendeley through their web importer clicking on a bookmark when I view the paper at the publisher's website