Google Reader feature request

I really enjoy using Google Reader as my online feed reader. But I just realized I wanted to do something that isn’t currently supported. Not sure whether this needs to be baked into the Google Reader code, or is doable via a Greasemonkey script: I want to be able to expand a feed (or a folder) and filter the items in the reader window by tag/category. When I’m not in a position to read everything in my reader (which is pretty much always), it would be really cool to be able to drill down just to the stuff that was highest value, regardless of the publisher.

So, lazy web… how about it?