>>nsoonh+(OP)
Maybe with the power of a supercomputer, Mathematica can finally launch in less than 30s. I have no idea how a software that still does essentially the same thing as it did in 1988 can be that sluggish.
>>pjmlp+R7
Sage Math? Though I admit, unlike homogeneous Mathematica, it's just a Python glue on multiple smaller projects of different quality and poorly integrated. I wish there was something more like the Wolfram software but there isn't.
>>xvilka+u8
I tried Sage Math. Just the fact that one has to declare all variables before using them, makes it extremely annoying. In Mathematica, I frequently do computations which have a couple of dozen variables. I am not going to write boiler plate for 20 different variables in every notebook.