I doubt anything. It's a mashup of various languages, broken interfaces and hilarious bugs.

Here's some of my favourites that I've encountered in my use of their pathetic products:

http://bad-adobe.tumblr.com/post/35671000643/

http://bad-adobe.tumblr.com/post/57065003458/

http://bad-adobe.tumblr.com/post/54814875332/

http://bad-adobe.tumblr.com/post/53922218860/

I don't think you'll find many people who haven't had the monolithic application completely fail on them at one point or another, inevitably during critical or expensive work.

The internals are probably pretty interesting but what's missing from other similar programs is the UX, GIMP is a giant papercut, I'm often tempted to edit images with emacs/imagemagick instead. Photoshop isn't perfect but it's really smooth to use.

One of the biggest lessons that any Adobe developer will tell you is "we're proud of the code and that it hasn't needed a rewrite - but if we were doing it from scratch we'd do it way different."

A great read on that conversation is http://blogs.adobe.com/jnack/2009/05/some_thoughts_about_the.... But I doubt anything insightful will come out of this leak along the same veins as we leaned when HL2 leaked.