I use RollerMouse Free 2 and have been using various RollerMouse units for several years. Over the last 3-4 years on GH, I've seen almost all people that use these units get completely spoiled. The few that don't care for it are usually doing CAD/Photoshop or other high precision work, or gamers.
I like RollerMouse, LARGE super-functional trackballs (Kensington Expert Mouse Pro, etc), touch/trackpads. I don't care for mice.