UPDATE. Thanks to Debbie Aboud, the very helpful sales executive at Contour Design, who is letting me free-trial both the Pro 2, and the Free 2 at the same time. :biggrin:
The Rollermouse Pro 2 is as good as promised. It places less static stress on your hands than any full-size trackball; it's more agile than a thumb trackball; and it allows you to move the pointer with one hand and click with the other, which is delightful. (It's difficult to hold a trackball steady while clicking buttons with the same hand!)
The default Pro 2 palm rest is not large enough. If you use your index and middle fingers on the roller, as I want to, that will push your palm off its perch and into an awkward posture. Luckily Contour makes a larger palm rest for the Pro and Pro 2, called the Rollerwave. Debbie is sending me a Rollerwave too. Thanks Debbie!
The Contour folks are nice, and the product is excellent. I'm probably just going to buy all of this stuff at the end of the month.
The default Free 2 palm rest is deeper to begin with. It looks like it's designed for index/middle finger use right out of the box.
The Free 2 has some other possible advantages over the Pro 2. It's narrower left-to-right, to work better with laptops and probably compact keyboards. Its keyboard lifter is totally detachable (I think... judging from pictures) so that will play nicer with the Kinesis. I'd rather not need to shim my Kinesis just because an unnecessary keyboard lifter made it wobble.
The Free 2 should be here next week some time. Look forward to two reviews... COMING SOON!