I also have the Lift vertical, for use when travelling, but it's not nearly as nice as the MX.
edit: also the Ergo keyboard is fantastic. I can't overstate how using ergonomic keyboard/mouse is important; you're using them basically all day.
As long as you are not using the mouse to draw (photoshop, gis software, cad software etc...) you will adapt. And the thingy is comfortable to use.
If you need to do some of those tasks that requires drawing a polygon, snap vertex into other things etc... The MX Ergo is not for you. You can do it, but you will be significantly more slow, even after months of practice. Look something else. I wish someone would have told me this before.
I have tried a number of trackballs, and haven't been able to reach the precision of a regular mouse from any — after a week of usage of each of several trackballs I only got to the convenience/precision of trackpoint or bad touchpad.
Moving in straight lines, predictable directions and moving just a few pixels was the biggest issue.