I think the main problem octave faces is matlab's libraries (such as simulink) which have no comparable open source or even free alternatives, that and writing matlab code sucks for anything bigger than a 50 or 100 lines.
Anyone that isn't using those could probably switch to octave with few issues but last time I checked some functions were starting to differ (see eig)
Octave is nice when you really need to have matlab compatible files but don't have a matlab license but now everyone that I know in the sciences if they are not using matlab and don't need to use fortran/c/c++ they are using python because why keep the matlab syntax if you can gain so much by switching to another language.
EDIT:
Also, although it's not opensource, I had used Mentor SystemVision eons ago in college. It now has a free web interface. I haven't tried it, but honestly, what could be worse than DxDesigner ;-)
Anyone that isn't using those could probably switch to octave with few issues but last time I checked some functions were starting to differ (see eig)
Octave is nice when you really need to have matlab compatible files but don't have a matlab license but now everyone that I know in the sciences if they are not using matlab and don't need to use fortran/c/c++ they are using python because why keep the matlab syntax if you can gain so much by switching to another language.