The main attraction of Microsoft's newest (dubbed "version 2.0") Wireless IntelliMouse Explorer and Wireless Optical Mouse ($45), however, isn't how they look. It's how they scroll -- horizontally as well as vertically, thanks to what Microsoft calls Tilt Wheel Technology: a scroll wheel that rocks from side to side as well as rolling forward and backward. To move left or right through a vast expanse of spreadsheet columns or sideways through an extra-wide Web page or other document, you can push the wheel to the side without having to move the mouse itself.
The company's IntelliPoint 5.0 driver offers separately adjustable vertical and horizontal scrolling speeds, defaulting to the slowest possible setting for both. That feels normal speedwise for scrolling up and down -- though we found it took some getting used to the new scroll wheel's smooth or continuous motion, without the detents or steps we're used to from other mice (e.g., two steps to scroll the Outlook calendar up an hour or one nudge to scroll a Word document down three lines).
By contrast, while the tilt wheel itself moves smoothly, horizontal scrolling is more herky-jerky or choppy unless you specify the fastest available rate. And the scroll wheel only moves along two axes -- your instinct at first touch is to see if you can also move diagonally, as if the wheel were an IBM ThinkPad pointing stick, but no go.
Still, after a bit of practice, the horizontal flow becomes intuitive and extremely convenient when navigating wide spreadsheets or artistically panoramic Web pages or zoomed-for-editing images. (With the more versatile scrolling, Microsoft even felt free to change the default "middle button" or click-the-wheel function from auto-scroll to an Alt-Tab-style switch between active applications.) But you won't use it often, if ever, for most Web browsing, word processing, e-mail, or other applications, unless you're restricted to a narrow window or low display resolution.
If only serious Excel addicts will really appreciate the tilt wheel (also found on the left edge of the keyboard of Microsoft's new $105 Wireless Optical Desktop Elite keyboard-and-mouse bundle), there are other reasons to enjoy the new Wireless IntelliMouse Explorer and Wireless Optical Mouse. One is their refined 27MHz radio-frequency technology, which not only uses 65,000 random security codes to avoid interference with other cordless devices but boasts Microsoft's most battery-efficient design yet. In fact, though we've hardly had our test unit long enough to confirm, the company claims that once you put a pair of AA alkalines (included) into each mouse, you won't need to replace them for five to six months.