My editor of choice for software development is Aquamacs. It's a Mac OS X version of Emacs that retains all the flexibility and power of Emacs but is a native Mac application that supports standard OS X shortcuts, look and feel.
The most recent version adds some nice new features, including the ability to open multiple files in tabs (similar to Safari or Firefox). However, one of the Emacs features which I rely on appears to have been changed. When I open a file, I expect a certain context highlighting style, depending on the type of file. Now, I am not an Emacs expert, but years ago I had defined the styles I liked and put them in my .emacs config file. When first switching to Aquamacs, I ended up dropping some of that info and using some of the many built in themes.
However, with this new release (1.4) it seems to ignore that information entirely, and opens files up in some default style. I am not clear why this behavior was changed. I had to dig around the Aquamacs site a bit to find the solution, and I thought I'd post it here, so it might help someone else.
The solution was to add an Aquamacs-specific line to the bottom of my .emacs:
(setq aquamacs-styles-mode t)
This made Aquamacs once again honor the style information I had set.