I find that I'm more productive prototyping algorithms in Matlab than in Python. In fact, I tend to write it first in Matlab, port it to Python, and finally port it to C (to run on an embedded device)!
As for Octave, I've used it a couple times in the past but found the environment underwhelming (especially so when creating plots). I also tend to run into various compatibility problems when running scripts developed in Matlab.