I've posted the feature request here:
http://code.google.com/p/pnotepad/issues/detail?id=82
I'd love to have an additional box in the "Find in Files" dialog labeled "Exclude file types". That way I could put ".svn" or ".pyc" in there and not see those in my results.
What do you guys think? Honestly, I'd love to optionally be able to put regex in there, since sometimes I want to exclude files depending on the filename (not extension). But extension-based filtering would be a great first-step.