The chief innovation of the MX Revolution is its scroll button. It functions in both the typical incremental click style, but also as a free-spinning wheel. This means you can whip the wheel frontward and back and navigate hundreds of pages in a document with a single spin. It's a little touchy when you zero it in on a particular page; sometimes moving your finger from it will make it jump another line or two, which can be irritating. But mostly, the free-spinning capability makes it much easier to scroll through long documents and Web pages.
In addition to the main scrollwheel, it also features a thumb-side wheel (the mouse is designed for righties). This side wheel acts like a rocker switch. It has a limited range of motion, but it's not designed for scrolling. It's meant to act as an application switcher. Roll it, and it brings up a small window listing all of your currently applications. You tap the wheel to move between them and press it to make a selection, at which point that app becomes your active window. It provides a remarkably easy way to switch between tasks, as long as your desktop setup is straightforward. On a system with two monitors and with multiple Firefox tabs open, we found keeping track of which screen was going to open up where a little difficult at first. Eventually, we got used to it.
Aside from the wheels, the MX Revolution is a relatively basic laser mouse in an extremely comfortable shell that has most of the features you'd expect. The two thumb-side buttons are smaller than on many other mice, but they're no less convenient to press for moving backward and forward between Web pages. At times they didn't register when we thought we'd pressed them, though, so the button sensitivity could use some tweaking, and that is not a setting you can change in Logitech's SetPoint software.
We were also a bit disappointed to see that the MX Revolution has no option to tweak the laser sensor's sensitivity on the fly. Perhaps Logitech considers that feature more appropriate to gaming mice, but for $99, we'd like to see such an option included. We imagine that designers and others, in addition to gamers, would appreciate the ability to switch cursor sensitivity without going into the mouse software. Logitech could have used the small button that sits under the scrollwheel for this. Right now, it's designed to call up the search engine of your choice, but we never found that capability particularly useful.