I use it here and there for interfacing with Maya, when MEL won't do the job. One of our artists here at SD writes all his tools in Python, it is very powerful in combination with Maya and MEL.
3dsmax supports python as well and just like in mel (maya) you can combine python with maxscript. I heard some developers saying that often they would code core functions and classes in python and with mel/maxscript/blender python they would then add the final interfaces or integration into the 3d tools. Just on a…