This looks like a cool idea. I think a couple of (neat!) examples, stuff you can't easily do with normal grep, will go a very long way. The list of features is secondary in my opinion.
You basically had this with the Smalltalk refactoring Browser, where each search popped up displayed in a browser window. Then you could easily AND such searches together by executing a script in the browser window. Slightly more sophisticated combinations were possible with just a few lines of scripting.
On top of that, everything above applied to syntax-driven rewrites and refactorings.
