FWIW weka is a well-designed system works great for many tasks. Especially if the user cannot code.
this looks... too good to be true. there's no way a free piece of software has all of these features and actually works. but really outside of educational purposes I don't see the use case. serious users will reach for R or python or even Matlab. but it looks great for teaching a high school data analysis class (or something like that).
It's made at the University of Ljubljana so educational purposes are probably high on the list of requirements.
I like how their interface is similar to Grasshopper's graphical algorithm editor for Rhino 3-D.