I had an interesting thing happen with numb hands recently. I bought a new frame and decided to try Grant Petersen's idea of having the bars even with the saddle. I did two rides of about 32 miles each and suffered with numb hands. I could not find a position on the bars that relieved the numbness. I flipped the stem which placed the bar a couple of inches below the saddle. No more numbness...

That seems really counterintuitive to me but, having tried riding with the high bars I can tell you, it stinks. I am more convinced than ever that either Grant doesn't really ride or he must be anatomically wierd. I haven't found any of his bike fit advice to pass the giggle test.