We're pretty much past the time of having to worry about response times when comparing LCDs. From what I've seen recently, any modern LCD has less than a 12ms or so response time, and the human eye really can't tell a difference once you drop below 14ms or 16ms. 4ms, 5ms, 8ms, 10ms...it doesn't really matter. I'm quite certain the new iMacs have a fast enough response time. Video on them looks gorgeous.