The Orbit Trackball’s a little smaller in dimension than most trackballs, including Kensington's own Slimblade Trackball. You'll still need a fair amount of desk space put aside for it, but unlike a regular mouse you won't need to move it at all, giving it somewhat fixed dimensions.
We say "somewhat fixed dimensions" because Kensington supplies a soft rubber wrist rest with the Orbit Trackball. It doesn't so much affix to the base of the Orbit as pretty much just sit there plopped onto the base, but again, as a trackball this isn't a particular problem as all the moving parts are contained around the bright blue trackball itself.
The design of the Orbit ball makes it stand out from the trackball crowd, which traditionally goes for a bright red design that usually ends up giving off a distinct Hal 9000 vibe. The electric blue tinge of the Orbit ball has more of a low-budget fan-made Star Trek film feel to it, if that's your sort of thing.
The Orbit Trackball uses a single red optical sensor to detect the movements of the blue sphere itself, flanked by two standard mouse buttons. Unlike the Slimblade, there's no additional buttons on offer here, although you can define an action for both mouse buttons pressed simultaneously. Those who don't like messy cables may be annoyed by the fact that the Orbit is tethered by a USB cable.
What makes the Orbit Trackball stand-out is what Kensington has stuck around the trackball itself: a scroll wheel. This is something that trackballs have struggled with for some time; while it's feasible to set up scroll wheel-style action to a dedicated button, it requires generally more finger dexterity than most users have or wish to utilise. By ringing the entire ball with a scroll wheel, it's always easily reached by hand. Or, in this case, fingertips.
One interesting omission that Kensington makes with the Orbit's packaging is the lack of software. Kensington's dedicated Trackball drivers, dubbed TrackballWorks (Windows XP, Vista, 7 and Mac OS) are available via download only, which could be annoying if you wanted the extra features on a system that lack Internet access.
For some users, a trackball represents the only real option due to physical mobility issues. Others may like a trackball simply because they represent a fixed way to perform basic mousing tasks. Whatever your take, in most respects the Orbit is just a regular trackball with regular features.
One thing that's arguably not a feature, but well worth mentioning to non-trackball users is that the blue trackball pops out easily, and if you're stuck for inspiration it's great to juggle from hand to hand in order to catch your muse. Just don't throw it at anyone. It's very solid.
In testing, we found the wrist rest comfortable despite the fact that it added considerable size to the overall unit, and quickly worked out a comfortable position for our hand to sit in so that both buttons were accessible with thumb and pinky finger. While the scroll wheel runs the whole way around the trackball base, we found the ring finger to be the most comfortable way to access it.
A trackball's still not for everyone. There are areas where a trackball can be harder to use than a regular mouse. Gaming's the most obvious case-point, depending on the style of games you like to play.
Trackballs remain a niche product, partly due to the different set of mousing skills they supply, partly due to the price premium that most trackballs command and partly due to the lack of feature parity with even the cheapest mice. The Kensington Orbit Trackball with Scroll Ring does a great job of covering the scroll wheel problem while being sold at a very affordable price point. The funky design is an extra plus. It's still a niche product that won't appeal to everyone, but if you're a regular trackball user, or figure one could aid your productivity or lessen your wrist pain, the Orbit Trackball is highly recommended.