Out of curiosity I've checked, among my applications, how many take advantage, or don't, of text substitution. This is the result:

Do: 1Password.app, Alfred 2.app, Bento.app, Calendar.app, Contacts.app, eMaps.app, iKey.app, Mail.app, Notes.app, Reminders.app, Safari.app, Skype.app, Textedit, Textexpander.

Don't: Find Any File.app, Firefox, iWorks (keynote, numbers, pages), Stickies, Yojimbo. (Surprisingly [?] none of Apple's iWorks.)