Confirmed again, same here.
Experimental build is UNPLAYABLE for me. No matter what server. I tried changing the movement keys (f,g,h,t instead of a,s,d,w) but I didn't help.
As people already said, the game behaves as if one of your keys was "stuck". My character keeps running to the right, unless I keep pressing the left key which will then cause the char to stand still.
Win 7 64B, Core i5 @ 2500, 8GB Ram, Radeon HD6870, R.A.T. 7 Gaming mouse