Tex-Edit Plus, http://www.tex-edit.com/ , is my favourite. Its Applescript support is invaluable, along with a huge archive of scripts and lessons on scripting it at http://www.malcolmadams.com/te/ .
While it's lacking a few things I'd like, such as Smultron's drawer or Web Preview it does have a script for previewing in the default browser. The scripts toolbar provides buttons for selected scripts.
It handles grep searching (with some excellent help files), and can search all open windows. It'll undo back past a save too.
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