I got a Studio a few weeks ago and am using the Kensington Pro Fit Ergo Vertical Wireless Trackball (K75326WW) from my Windows PC. I like that I can just hit a switch to toggle between the two machines.
Before the Kensington, I had a Logitech M570 trackball. It was great, but the button switches wore out after a couple of years. I chose the Kensington after reading that it uses more durable switches. After about 2.5 years of daily use, they're still going strong. However, the scroll wheel optical sensor appears to be failing because it jumps a lot, even with a fresh battery.
I love trackball mice, but each one seems to have its flaws.