I have been working at my corner desk for two months now. I have the 3-legged set up with the extension top.
The motor: Smooth and much more quiet than i thought. I can have a full glass of water on the desktop and move the desk up or down without so much as a ripple in the glass.
Stability: Very stable. The frame is solid and heavy, with a low center of gravity.
The tops: Nothing fancy. I have the beech finish. It's a pretty regular MDF top.
Assembly instructions: Not the greatest detail in the world, but I figured it out. I would definitely recommend that you have 2 people put the desk together, especially if you order the big top sizes like I did.
Overall: I would give it a 9/10. The value and build quality of the frame are excellent.