@ARTICLE{AlmironSilvaMM:2009,
author = {Almiron, M. and Almeida, E. S. and Miranda, M.},
title = {The Reliability of Statistical Functions in Four Software
Packages Freely used in Numerical Computation},
journal = {Brazilian Journal of Probability and Statistics},
year = {in press},
volume = {Special Issue on Statistical Image and Signal Processing},
url = {http://www.imstat.org/bjps/}}
is freely available under the "Future Papers" link. It makes a nice
comparison of the numerical properties of R, Ox, Octave and Python.