I have been using the 27'' iMac for 2 weeks, and I have been getting a serious headache with nausea every time I used it for more than 20 minutes or so. I have notice that I had to extend my neck in order to read the upper portion of the display. The display is gorgeous, by the way. I am 5'10'', and I can only raise the chair so high before my knee started touching the underside of the table with minor movements and that the chair edge started to compress the underside of my thighs. Since the height of the display is not adjustable, I see no solution to this problem. I am in the process of exchanging for a 21'' iMac. Hopefully with the display being 3'' shorter, it would resolve the problem for me. Has anyone had similar experience?