It's real cool until the wheel switch picks up a little crud and your pages start to jump around when you DON'T want them too. I do use it, but rarely. Seems like I stay familiar with it more because it works when it shouldn't than from using it intentionally.
Of course, maybe it's just that my mouse doesn't digest the coffee spills and cookies crumbs it eats rolling around my (only slightly cluttered) workspace. I suppose a good (well fed) mouse deserves to retire after a dozen years or so, but...