I keep my Firefox up to date with release versions, have few plugins, and still find it absorbing memory at a tremendous rate. Chrome can also use memory, but somehow manages to let it go sometimes, as well as not drag my entire (Windows) system to a stutter.

I guess so many of us mention FF in this context because it still happens to us, even though we gamely continue to use it. But we still love it, and that's why we continue to use it. Though admittedly, most of us have a Chrome on the side...