Put me in the emacs camp!
 

I use emacs on OSX, I have been using the midelube package, but have recently had success with compiling form cvs..

Either way I find it a super editor, while you may not be able to drag and drop, I find the [click, double right click -> middle click] cut and paste works very well. but to each his own. ;)

And paticularly on topic - if you want insert key functionality with emacs, it's easy. Just put the following in your ~/.emacs:

(global-set-key "\M-z" 'overwrite-mode)

Replace M-z with the command of your choice and have fun.