Rating: 
Summary: Excellent trackball
Review: Like many reviewers, I had tried many different mice and found a tendency to hand and finger fatigue with prolonged use, as well the nuisance of falling off the mousepad periodically.After having a Kensington trackball for use at workstations in our hospital, I became gradually used to the feel of this trackball which initially was irritating regarding pointing accurately. Once having become used to it, I have found it just as fast and accurate as a mouse, and relatively effortless especially when using it for hours at a time. The stationary aspect is a welcome relief, and you develop the eye-finger coordination very quickly. The software is excellent and allows virtually any type of programming of all the buttons plus two additional "double button" selections(pressing two buttons at a time). While you can program a button to scroll or autoscroll, this is generally unnecessary since there is an additional scroll ring which can be programmed in either direction, at several rates. The unit is equally easily used right or left handed. Another plus for me is that I can place it directly on my Wacom tablet, while optical cordless mice I have found to suffer from interference, I presume RF, from the tablet, so that an intervening mouse pad is required. Not so for the Kensington trackball. I have found no conflict with the Wacom and Kensington drivers. I initially experienced periodic spontaneous reversion of the button programming to default positions, but this bug seems to have been corrected with the latest iteration of the driver. This trackball does eat batteries(2 C cells) which must be replaced about every month with standard usage. In talking with tech support, they say that it is because of the high resolution, and that it indeed does power down when not used, but I wonder if the batteries wouldn't last longer if there were an off switch, or that electronically it would switch to a real hibernate mode when not used for a programmable period of time. It's not a big deal, but plan to add about $25/year for operating costs! Not inexpensive, for sure, but, IMHO, well worth the investment in terms of ease of use and its features. For those who have not used a trackball, please be prepared to spend a little time getting used to its format, feeling clumsy a bit at first, and not rushing to judgment. Buying from a place with a 30 day exchange period would seem reasonable.
Rating: 
Summary: Could not keep it working
Review: Within a month of getting this. It stopped working. After dealing with Tech Support, they sent me a second one. It also stopped working after about a month. I tried to convince the woman in India (Kensington customer service) to replace it with a less expensive, wired trackball that worked, and they refused.
It was nice while it worked, but but died far too quickly.
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