I use emacs in a terminal window for probably 75% of my editing, and textmate for the other 25- I have Aquamacs but couldn't get into the flow with it for some reason. I keep all the default keys for ctrl/etc, and it does help a bit that they newest macs have changed the enter key that used to be to the right of spacebar to alt.
While it's not really emacs, I generally do most of my development in Eclipse- but I change the keybindings to Emacs mode (window\preferences\general\keys). Makes eclipse almost nice to use.
I tried setting IntelliJ IDEA to Emacs key bindings, but I had to switch back to the default bindings. With the Emacs-like key bindings my fingers automatically expected a lot of things to work that IDEA plainly did not support (like kill ring).
My preference when I am not using Emacs is to make a clean break so my finger macros don't run wild, often unintentionally pressing key bindings that do other things than I expect.
While it's not really emacs, I generally do most of my development in Eclipse- but I change the keybindings to Emacs mode (window\preferences\general\keys). Makes eclipse almost nice to use.