The bigest advantage was the click buttons did not have the double click problem that Logitech's MX-Ergo Trackball does. It also tends to reduce the false click problem that Nuela's M514 has. It has the same DPI ajustment and 3 connection options on the bottom of the unit. Easier to select over what the M514 interface has.

But this M511 is less comfortable than it's cousin M514. I found the M514 more comfortble to use once you get use to it.

The awkward thing about the mount it it easily separates from the track ball. There's no Velcro stickums nor magnet to secure the base.