[nawitus]

Interesting features, but I feel like it's a lost cause, as it's not worth investing in a proprietary platform.

[j2kun]

Tell that to the millions of engineers that invest in Matlab. But seriously, I've found lots of use for Mathematica's visualization techniques whose results (images and animations) are certainly platform independent.

[gress]

What platform is not proprietary?

[ISL]

Octave, SciPy, etc.

I'm not aware of a replacement for Mathematica's symbolic manipulation that's even close. It's good enough that it's scared any pretenders out of the castle.