Hello, 
 
I'm trying Scientific WorkPlace under MS Windows. I probably won't buy it because : 
- it's too expensive 
- it runs only under Windows 
- it's not open source. 
 
But one feature is very usefull : having a computation engine when writing
a document. Mathcad has a similar feature (but is not really a word processing) 
 
I know some good computation engine  
for numerical calculus : Scilab, Octave... 
for formal calculus : Xcas/GIAC(*) / GINAC / Macsima or Maxima / SAGEMATH 
 
I really think that adding a computation feature can be very usefull because you
could easily change numerical values and everythings after will be changed. So
it can be usefull for writing Math/Physic exams and corrections.
I know such a feature will not be use by several people (only scientist) so I
think that it should be add as an extension.
 
Kind regards 
 
PS : some experiments was made using GIAC and LaTeX and describe at 
http://www-fourier.ujf-grenoble.fr/~parisse/giac_fr.html#latex