I used it somewhat this way but also subscribed to some big prolific sites that I don't happen to visit that often and then once in awhile, in Reader, I'd glance at the newest 50 items in their list. I didn't have a problem ignoring > 50% of the feeds in my list but still keeping them in my list.

I'd read the feeds I most care about and once in awhile visit the ones I less cared about.

I loved Bloglines and only reluctantly switched to Reader. Like you I mostly used it as a way to check less prolific blogs including blogs by friends and family.