http://www.tomshardware.co.uk/3d-polarized-projector,review-31849.html
FTA:
Alternate-frame sequencing is the method of 3D realization that we used in 2007 when we put together the "Wall-Sized 3D Displays: The Ultimate Gaming Room" article. Back then, 120 Hz projectors were practically unheard of, so we settled for an 80 Hz DLP projector. This projector could display 80 FPS, delivering 40 frames for each eye. While 40 frames per eye aren’t bad, at the slower shutter speed, the strobe effect is far more pronounced. This strobe effect can make it hard to watch a 3D display for long periods of time and may cause disorientation and headaches. The issue was more acceptable three years ago when intrepid early-adopters were pioneering wall-sized 3D viewing, but it wouldn't cut it in today's mass market. It's 2010 and we expect more.
I was wondering about the OP's question myself. I'll take his word for it, though it would be nice to see an example in person to see how distracting this "strobe effect" really is.