I am an experienced Kennsington trackball user and find that their products have matured nicely over time. They now have a hole in the bottom so that dust and hair will fall out onto the desk instead of accumulate in a wad that causes malfunction. This model is a bit on the small side and the buttons as well could be a little bigger, but the size is usable. The action and heft of the ball are just right, very smooth and feather touch.

But the biggest (very big) complaint is the stalling, reported in previous reviews. It is not dirt--It's the patterning on the trackball. The swirls are broken by a solid area and the optical sensor has difficulty in picking up movement in that area. Every time it stalls, I look at the ball and note that this area is over the sensor. This is a big deal and very annoying in normal operation. There needs to be a recall and redesign.

This is one of the best trackball I've used. Being a graphic designer I've always been using trackballs, they are very convenient in using on your desk specially when you have your desk well cluttered with other items. In addition you can use a trackball on any surface, you don't have to worry about finding an even flat space to move your mouse. Comparing to various trackballs available in the market, this Orbit from Kensington is the best one at very low price and it's cosmetic outlook is also well impressive as its very precise optical tracking ability. I would highly recommend this for anyone who is looking for a trackball at low price.

Good product. I think it would be a better mouse if it had a scroll wheel.

This mouse is OK but certainly not great. It's very light, so moves around alot, The buttons are placed a little odd for easy use if your hand is placed so that the fingers can use the trackball properly. The design has tried to make the buttons look good instead of making them more useful. They are also a little hard to press for quick use because the shape gets small where my thumb would normally rest so I have to hit it just right to get it to work. It's really not big enough to hold your hand properly so you don't get any repetitive motion problems. Unless you've got really small hands, you're probably going to find yourself holding your finger joints UP so your fingertips can work the ball. My hand doesn't rest easy in that position. After several days of trying to make it work for me, I'm sending it back actually. I was replacing a well used Kensington Turbo Mouse, and find that I just need to bite the price bullet and get the Expert Mouse

I used the old ADB version before this one and they're both amazing. It's the only mouse that keeps my wrist from hurting after multiple long days of work.
Some of the finish gradually wears off, but mine is still working 100% after having it for 4+ years, and only needs cleaning every few weeks.
I've tried finding a different mouse several times, just to try something different (or something with more buttons, scroll wheel, etc) and every time end up back with the Orbit.
Something to note, is that it's not a trackball - you don't control it with your palm. You only use your fingertips, allowing you to put your arm and hand in a comfortable position and leave them there.