It's an awesome language for non programming peons. It's absolutely awesome for statistics, it's relatively easy to use, there's a package for everything. Why do people like to h@te on R?
I think overall R is well liked, compared to Stata and Matlab at least, because it is free (as in freedom), as a huge amount of libraries for all statistical things and can even to an extent serve as a general purpose scripting language like Python. R is too slow for serious numerical work however. For the latter C/C++ or Fortran are mandatory.
EJMR always talks about speed because they have no idea what actually differentiates languages.
Idk what people here do but I've never had issues with speed
Here is a simple example: implement a particle filter in R (or Python). Depending on the data set and model complexity (including the cost of evaluating the model), a single run of the particle filter may take several seconds. Now imagine you need to run the filter one million times, e.g. to estimate the model. In such cases a compiled code may slash the running time by a factor of 100, and the resulting procedure may still take several days to run. That would be several months in R or Python.