(2) It has a huge repositoriy of libraries. There's hardly anything that you can't do with R. In my special case it was about hazard-rate models, which are barely implemented in other tools that I tried (namely EViews, SPSS)
(3) It has a BIG community behind it, which you can ask for help once you're stuck. I haven't found this kind of "service" in other software (namely, again, EViews).
Almost the only reason you'd need to use R. I cringe when professors ask their students to use non-free software when equivalent or better free alternative exist.
