I use more and more emacs for my hacking activities. I am more used to Netbeans and Eclipse IDEs but the possibility to do anything from only one editor attracts me....
One thing I miss however currently is the possibility to organize my files as a project. Typically if I develop a PHP application, I'd like to be able to a)navigate in the current file to jump directly to a class' member (either variable, function, whatever) and b) jump into a dependency, this can be a superclass or a class from a library I use, anything. Doing that from my beloved IDEs is very easy, but from Emacs I read about tags, anything and certainly others...