In the Sony HW50 owners thread I've seen very few complain about motion with the Sony, but there have been a couple. Personally my unit does motion flawlessly with all my sources. I dare to say even better then my Infocus X10.
The only issues I've seen with motion judder on the HW50 have been using film mode. I think someone in the HW50 thread mentioned something about an incorrect 3:2 pulldown?! In any case, I watch a ton of sports on my HW50 and motion judder is something that I'm particularly sensitive to (think zombie and black levels)! I can say the Sony handles motion very well if setup correctly.