I would recommend Gephi for easy ramp-up and fast graph visualization, especially for SNA (Social Network Analysis) and community discovery in general. It makes it easy to experiment with new techniques and explore your data intuitively, and even intuitively evaluate some more advanced techniques like clustering. However, if the user is already pretty advanced in graph analysis or wants specific algorithms and functions, they should look to see whether those exist in Gephi plug-ins and compare it to plug-ins in R, Cytoscape, yEd and other data visualization solutions. In particular, I have found that Tulip, although, harder to learn at first, fills many of the gaps left by Gephi. Still, it is so easy to get started on Gephi that I might still recommend it to someone who knows they will need a more sophisticated product like Tulip down-the-road.