I started a thread called rotex fun. I had the RO-90 and went to town on a floor with it. Yes a floor. 8 hours in I could palm the ro90. By the end of the second day my wrists were so sore I had to wear wrist braces for two weeks and another week just relaxing them Then I was at it again. the first hour and half was hell trying to get that little beast in rotex mode to behave. I can now one hand the ro90 and bought an ro150. When I first tired the ro150 I was thinking I should have bought it to start with it was so easy to use in comparison. I kept both and love both but there is a steep learning curve to the little ro90. I imagine the ro125 to be somewhere in-between the ro90 and ro150 in use of handling. It is all about the balance point and the torque your wrist introduces to the unit while trying to hold it steady. I actually found the orbital mode harder to use on the 150 than the rotex mode. wired I know. Stick with it, it is worth it.