While I think Python is great, I think the author discounts R too casually. I share his frustrations about R, but what's nice is R (well, S) was designed to be a statistical computing tool, and it does anything related to that quite well. Especially for data analysis, which is where I spend a lot of my time (perhaps most) in the whole model building process, R is amazing. Also, R is very usable out of the box for math and data visualization, whereas Python requires many libraries. It's good to know R.

I think R and Python can be used in conjunction very effectively. Analyze your data in R, prototype your algorithms in either, build products in Python.