This is the killer feature of tools like emacs and vi: Your vendor cannot abandon you and the code has a well-proven capability to be ported to just about any platform.
The cross-platform aspects of these tools is way undersold. I have all my config checked in at BitBucket. I can sit down at a new machine, check out my emacs configuration, tweak a couple variables if things are non-standard on the box (paths and the like), and I've got my environment completely set up, whether Mac, Windows, Linux, or something else.
I completely agree with this. Emacs is an amazing environment that can be customized and extended in so many ways. It also has support for just about anything you'd ever want to do.
It's also nice that you don't have to have N dev environments installed to support each language you want to play with. I work in Java, C++, Python, Erlang, HTML, JavaScript, and Ruby fairly regularly. Installing and learning a completely new environment for each would be obnoxious.