Agreed. I use Python for heavy shell-scripting and text-processing (though R surprisingly does have respectable facilities for all but the most overwhelming of these tasks) and R for the rest of the analysis. I've thought about switching to NumPy/SciPy as it's part of Python to integrate everything, but R's data frame, factors, and reshape, plyr, and lattice packages makes you think very differently about how to approach the data - and hard to go back to lower-level manipulation of arrays; not to mention all the stats/graphics packages which are very easy to install and apply. And documentation of its functions is superb.