Jan, Most of my opinions of programming languages are based on feel and trust, which means it's all subjective. I don't care for Mathematica in terms of its brittleness -- when I was using it regularly it would freeze my PC. When I looked at it closely, it was actually running in some sort of kernel mode -- I'm assuming just to get that last ounce of performance. That's a bit beyond my comfort level. It is impressive because they do go for the neat bells & whistles whenever they can. The syntax is a bit too read-only for me.
I get what you are saying about R. In the past I have R integrated into another executable just to get a specific library call. But then I noticed that it was leaving a never-ending chain of defunct processes, which wasn't so good :( Overall, I don't like the feel of the R syntax either.
When I look at a language I first try to decide whether it is procedural, functional, and declarative, or some mix. Julia is a mix, while a language such as Haskell is more purely functional. I am at the point of being more interested in solving problems and trying to pick the right programming approach to apply.