I've been using this Kensington trackball on my desktop for a little less than a year now (I'm using no less than 4 logitech vx revolutions on my various laptops!) and I can say that with a few exceptions most aspects of it are amazing!
First of all trackballs in general are simply phenomenal in comfort. Your friends may gape and wonder why anyone is still using a trackball in this day and age, but the advantages are undeniable.
You should buy a trackball in general because...
o Saves desktop space - you don't have to wave your hand around on a cluttered desk as with a mouse.
o Pain free - Your wrists, and joints ache less since trackballs are so ergonomic. This equates to more productivity!
o Programmable - A lot of mice are too but not the cheaper ones.
o Really hard to lose - unlike wireless mice.
o Cool factor - Trackballs look cool partly because they are somewhat of a rarity. A trackball shows you take care of yourself when computing. There's a reason why graphic artists prefer trackballs over mice.
On top of those general benefits, my Kensington Expert Trackball always surprises me with it's precision. With my Logitech VX revolution - which I also consider to be one of mankind's best inventions, I'm always hunting for the right place to put my cursor to click on a button, or to find a scroll bar etc. With the Kensington Expert Trackball, I realize that I don't do that at all. The pointer always goes where I want it to go. Without fail. If I need to make an adjustment, I just need to wiggle my index finger a bit and I'm golden. Funny thing is, I don't even notice how comfortable that precision is until I revert back to using a mouse, especially if that mouse is of lesser quality.
You should buy this Kensington Expert Trackball because
o Once you get used to it, it's really one of the most comfortable computing experiences you will ever encounter.
o It's really different and intuitive.
o It will help you do whatever you do faster and more efficiently