I finally replaced the Logitech trackball at my desk computer. It's "only" about a decade old, and has been in near daily use by me and at least one kid for most of that time. They don't make the corded version anymore, so I'm using the wireless version. Wow. The old one was really worn. This new one clicks much more decisively. More importantly, the buttons work all the time, rather than intermittently. I expect this will solve a few of the problems I've been having with cut-n-paste & layout work....