Yep. BBEdit from Bare Bones. They just came out with version 10 in July so, it's very mature, stable software that has tons of useful features.
http://www.barebones.com/products/bbedit/
BBEdit does multi-file search/replace. You can search folders too so, you don't actually have to open everything first. You can use GREP too if you want. BBEdit allows you to save search/replace patterns.
Also, it has a Compare tool to find/replace differences between two similar files.
It has Clippings so you can so you can insert common chunks of text. And, you can also write scripts to do multiple search/replace and other repetitive actions. And, can also assign your own keyboard shortcuts.
You can also edit remote files on a server via FTP.
BBEdit has customizable text coloring so it's easy to see differences between various tags, params, text, etc..
The new version 10 introductory price is $40 until Oct.19 then, I think it will be $50. Also available on Mac App Store although, command-line tools are not available in the Mac App Store version.
Bare Bones has very good support response and there's also a very active google group if you want help/advice from other BBEdit users.
Here's the BBEdit support page if you want to preview the manual and other app resources.
http://www.barebones.com/support/bbedit/
User group on google:
http://groups.google.com/group/bbedit
