Unix is an IDE. I do my development (Python web apps mostly) with Vim with a bunch of custom plugins, shell (in GNOME Terminal: tabs rule!), GNU make, ctags, find + grep, svn/bzr/hg/git. The current working directory is my project configuration/state. I run tests here (bin/test), I search for code here (vim -t TagName, find + grep), I run applications here (make run or bin/appname). I can multitask freely, for example, if I'm in the middle of typing an SVN commit message, I can hit Ctrl+Shift+T, get a new terminal tab in the same working directory, and look something up.