Trackballs are an acquired taste. Some look on them as oddities, but here's a confession: I've been using a trackball for well over a decade and find the arrangement comfortable and easy to work with. I also use an ergonomic keyboard, and I've never had a hint of RSI. Are the two factors related? Maybe, but I can't know for certain. But I do know the trackball as a format gets the thumbs-up from me, as it were.
Logitech Ergo M575 review at ZDNet