I have been using Julia extensively for about a year as a data analysis tool / R and Matlab replacement. I can say it is very good, especially well suited for exploring and processing large amounts of data. Often when you're trying to understand a set of data, you don't know what kinds of filters and transformations you're going to want to try. If those transformations end up not being easily vectorizable, then they will be dog slow to run in R or Matlab, and probably inconvenient and more difficult to create in C. For these situations, Julia is perfect.