I have been using these in both my cars for about a year. As much as I like them ( I did buy two) I wouldn't use one on my motorcycle without some tweaking. I've hit big enough bumps to dislodge my iPhone from the mount. Obviously in a car it's no big deal if it falls on a carpeted floor, on a motorcycle ??? If I did use one on a bike I would secure it with something, maybe a heavy duty rubber band. Great product with a bit of fiddling. (Posted on 6/26/12)
Most mounts for smartphones require you to take the phone out of the case... a real hassle. This little sucker will adapt to any case and hold on tight. The nubs are a firm sticky rubber that grab other rubbery and plastic surfaces very tightly.
I haven't tried mounting it to a paint shaker, but I'll bet it would hold. Got it mounted on my bike, and it's very sturdy. Haven't seen any shifting or movement.
Mounting it horizontally is the safest orientation, since the nubs cradle it from underneath, rather than just 'grasping' it if vertical. Also, the flatter you mount it (i.e. the device's face is parallel to the ground) the better it will hold. Common sense really.