This is an old mouse now, but it is still one of my favourites.
Under Windows 98 this mouse was amazing, and I was glad to see that Logitech provided OSX drivers when I switched to Macs - and that's where the fun ended. Logitech removed one piece of vital functionality from the drivers - the ability to set the orientation of the mouse. By this I mean the ability to 'tell' the mouse which direction of ball movement you think should be 'up'. I believe this feature was removed from Windows drivers at the same time, making this mouse unusable for me, as I didn't agree with the direction Logitech set as 'up'. This really is a vital part of mouse setup for a trackball, and I cannot imagine why they thought it would be a good idea to remove it (maybe it has been reinstated now - I don't know).
So, now the mouse lives on my old Windows 98 machine while all my other PCs/Macs have 'proper' Logitech mice, not trackballs. It sits in your hand perfectly and you can comfortably mouse on your lap or a desk etc. The ball pops out easily enough to occasionally clean the grime from the rollers (purely mechanical, as this is an optical mouse).
This trackball would be no real use to left-handers. It could do with an update too, as it has been around for many years. More buttons (at least Logitech's fwd/back buttons) are needed, and horizontal scrolling would be good too. The receiver unit is pretty vast by today's standards.
A great mouse in the good old days, but ruined for todays operating systems by poor drivers.