I use MJ for a lot of things, but I also still use a few other apps. I guess there are two reasons. First, sometimes the other apps are more capable in their specific area. For example, I use acoustica to edit wave files. I recently tried media editor, but I couldn't figure out how to apply a low-pass filter. I suppose you somehow send the process through the equalizer, but it wasn't obvious to me. Second, I can never quite tell if MJ is going to put my temporary work files into the MJ database. This can really screw up all the work I put into the database, so I just feel safer doing some things outside MJ. If MJ did all this stuff, and it was put in my face when I was working on external files and when the database was being changed, then I'd probably dump the other apps and do it all in MJ.
Scronch