Well I can say that my 6ms Samsung still blurrs ever so slightly after a few more adjustments and it might not blurr at all if in HD instead of SD and this is only when watching Football games and just the football when thrown or kicked, I have yet to see any blurring with any other sport. Now my father's Sharp at 4ms shows no bluring at anytime I have seen it in HD or SD so 4ms seems to be the barrier.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70