As a user of both MATLAB and R, I think they are very different applications. I myself have a background in computer science, etc. and I can't help thinking that R is by statisticians for statisticians whereas MATLAB is by programmers for programmers.
R makes it very easy to visualize and compute all sorts of statistical stuff but I wouldn't use it to implement anything signal processing related if it was up to me.
To sum up, if you want to do statistics, use R. If you want to program, use MATLAB or some programming language.
