I am a very, very satisfied customer! The big Anywhere selling-point is that its laser will work on any surface, even glass, and I can confirm that this is true on my desk, too. But that's now what I wanted it for: rather, I was interested in its novel scrolling wheel, which has two modes. Normally, it runs as a regular wheel, with a controlled spin that goes tick-tick-tick as your roll over it with your fingertip. But if you depress the wheel once, it releases its clutch, and then you just need to give it the lightest touch to set it spinning for a very long time, smoothly scrolling up or down until you touch it again. One more click-down and you re-engage the clutch (the middle mouse button has been moved from the wheel to slightly below it).
The wheel also acts as a side-scroll controller -- just tilt it left or right to make oversized web-pages scroll horizontally. This is a Fitt's Law godsend, bringing much-needed usability to badly designed overwide pages. The side of the mouse also has page-forward and page-back buttons, placed where they're easy to get at without getting in the way.
The Anywhere uses Logitech's novel (and tiny!) "Unifying" receiver, which runs at 2.4GHz (but has not noticeably interfered with my WiFi reception) and does not have the line-of-sight problems I experienced with the infrared receiver. It also has some clever power-management for travellers who are counting the ounces in their gear bag: it will run on a single AA battery, knocking 25g off the total weight (though it runs for longer if you load it with two AAs).
Best of all, the whole setup worked without any additional software, drivers or setup in my Ubuntu Linux Karmic Koala laptop. I just plugged it in and it worked -- no fuss, no muss. I don't know if that's because of Logitech's design or clever Ubuntu hackers, but I'm thankful for it (the mouse also came with some kind of software on a CD, but I just chucked that out).
This is a thoughtfully designed, genuinely useful addition to my computing setup. The fit and finish really shine, from the business with the battery to the surgical and deeply satisfying click that is the mouse equivalent of the chunk of a Mercedes door. I'm actually finding myself pining for the mouse when I'm away from my desk on my laptop, and am thinking of getting another for home.