I have been using [TextMate] as my editor for local work on my Mac for several years now. I like TextMate (and contributed to the Ethan Gutmann's IDL bundle for it); it is the most "Mac-like" editor I've found. But it definitely has some growing issues and has not been frequently updated over the years. MacroMates finally released the promised [TextMate 2 alpha] last December, but it lacked required features and development had been slow.
I thought last week's announcement that TextMate 2 was being [open sourced] was the death knell for TextMate 2 and that I would need to look for a replacement editor like [Chocolat] or [Sublime Text 2]. But there have been many [contributions][GitHub commits] to TextMate's [GitHub repo] in the last two weeks -- and new releases every day!
This is all to say that I have been working on an IDL bundle for TextMate 2, which I will put on GitHub shortly. It has very basic support for IDL syntax and there are plenty of bugs in it right now.
[TextMate]: http://macromates.com "TextMate - The Missing Editor for Mac OS X"
[TextMate 2 alpha]: http://blog.macromates.com/2011/textmate-2-0-alpha/ "TextMate 2.0 Alpha"
[open sourced]: http://blog.macromates.com/2012/textmate-2-at-github/ "TextMate 2 at GitHub"
[Chocolat]: http://chocolatapp.com "Chocolat < Text Editor for Mac" [Sublime Text 2]: http://www.sublimetext.com "Sublime Text: The text editor you'll fall in love with" [GitHub repo]: https://github.com/textmate/textmate "TextMate 2 on GitHub" [GitHub commits]: https://github.com/textmate/textmate/graphs/commit-activity "GitHub commits for TextMate 2"