Matlab, Scilab, Octave, R, etc

[RizzoTheRat]

I used Matlab and Simulink years ago at uni but am now interested in getting to grips with that kind of product for data analysis and possibly some system dynamics modelling without shelling out a fortune on licences before I know if it's actually worth learning rather than just using Excel/VBA. On first glance Scilab seems to make sense as Xcos will let me look at some systems dynamics modelling whereas I don't know of any equivalents for Octave or R.

Anyone know much about these and able to offer any thoughts?

[RizzoTheRat]

I wouldn't really say I had a Matlab background, my main memory was failing to work out how to use it an plot outputs in Uniras (or something like that) and programming my own analysis and graphics in Fortran 77