I'd completely forgotten this, though I have it as a preference pane. Thank you for reminding me.
SublimeText 2 is recognized in the app list, with a long list of extensions supported, with a single checkmark to add it as an "Open With" option to all of them and a button to allow making it the default.
(Note, it's not always what one wants as the default, consider .html for example, so more granular settings may be in order.)
http://www.rubicode.com/Software/RCDefaultApp/