Matlab is very stable and well tested. I can still run my first programs developed for Matlab 4.2 (1994), when I consider the handfull of changes in the core-functions. The methods for debugging are powerful, but the tools for code or project management are in its infancy. The documentation of the functions is near to perfect: clear help texts, exhaustive docs for each command, but unfortunately no version history to find out, in which release a specific command has been added or modified. But the Matlab community and the support are very helpful to clear such and other questions or problems.
I assume, that the integration of Java for the GUI elements reduces the compatibility in the far future. When you try to use smart UI controls like UITrees, UITables or UITabs, there are even incompatibilities in the last few years and the main part of them is not documented at all.
My conclusion: MATLAB is a good choice, if you want to create programs, which are very reliable, stable and platform independent, and use GUIs looking older than the Atari ST (1986). If you develop projects in a group, additional external management methods are required urgently (yes, Walter, I think the term is correct here).
I personally like the clear and compact notation of array operations. This reduces the size of my code by about 75% and makes dull indexing bugs less likely. I can discuss with other Matlab users about A + B without needing to specify, which compiler, compiler flags and libraries I'm using. While I frequently get mails of upset hardcore programmers, when I dare to use C-99 style // comments in a C-source code, the Matlab community is cool and concentrate on real problems (as long as the code is not spoiled by eval, clear all or global).