It's got to be more than just on SE though right? I mean, is there a city in the world where one person has a problem where another can't counter and say it works perfectly for them? If there is, I haven't seen it. Incompatibility with video drivers / graphic cards, ISPs, etc. can cause the problem. One day someone is going to pinpoint it; but there is rarely any discussion about it. Usually you'll just see people blaming SE without listing the ISP they use, the graphics card they use, the computer stats they use, etc.

It might be SE's fault. I'm not saying it isn't. It's just difficult to decipher the problem when someone from Australia, London, Florida, wherever complains about the lag and then someone else from the same area has absolutely no problem and has cleared coil.