As a recent Emacs convert I was able to develop happily for Android/Java, Ruby, Rails, Web, WordPress and ChucK, Octave music language, a lot of CSV/Data import tasks, and minor C/C++ edits. For each one I had used a lot of IDEs earlier.
As a long time emacs user, it's great to know that it can grow to support new languages and environments. I wasn't aware that it supports Octave (the music language). Welcome to emacs, we hope you enjoy your stay!
Do you mean this?