On the latest experimental build (0.62.139977), I experienced constant stuttering when trying to move while using the 64 bit client. Movement in any direction made the game freeze up for up to 5 seconds. This happened very frequently, so that I was unable to move, and made the game unplayable.
Deleting the contents of my C:\Users\*username*\Documents\DayZ folder did not solve the issue. I did not experience the issue while playing on the 32 bit client however.
I have attached a video that showcases the stuttering:
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