Summary: Logitech products have always serverd me well. I have never like the traditional mouse, that you have to move all over the place.
The ball rolls easily and I have excellent control over the pointer.
It is a cinch to clean.
If you like ease of movement and great control this is an excellent choice.
I preferr the model with the ball in the middle. My wife likes the thumb version which has a page scrolling wheel in the middle.
Summary: I use this trackball mouse every day. There is no comparison for stability, accuracy and speed. Once you've gotten used to a track ball you will not want to go back to chasing a regular mouse all over your desk. Your arm does not tire from that constant movement - on the contrary, there is no strain because your arm stays relaxed in one basic position.
Pros: Accurate Tracking, Comfortable Design, Fast Response, Great Features, Stable, Works On Any Surface
Summary: This is my first trackball. Got it a month ago. Using it on my laptop that comes with touchpad + "button" cursor. Learning Curve ============== - Less than 30 minutes to master the trackball-to-cursor coordination. - One hour to discover the joy of "throwing" the cursor across the screen with a light flick on the ball. (Don't try this with your mouse, especially the wireless ones.
Summary: There have been some comments posted here that "you don't need to clean it" or that "it works great without being cleaned". It DOES need to be cleaned, or the friction keeps going up. The good news is that this takes only about 15 seconds to do, and is nothing like digging cat hair out of mechanical gears with a long thin knife, which I've had to do before. There's a hole in the bottom. Stick a pencil eraser in there and push up. The ball will pop out.
Summary: My Trackman Marble+ went bad and I got this as a replacement. It just doesn't fit my hand as well. The Marble+ left my wrist above the surface the mouse rests on, but with this, half my palm rests on the table. It is higher in profile and steeper. It does not accommodate your entire hand. Another difference from the Marble+ is that the right-click button is clicked using the middle finger. Its good, but I miss my Marble+.