The original beater got put into the dishwasher, but seemed fine.  Then we moved and it got misplaced. I ordered a replacement (great way to find the original, btw!) and before I could tell my teenage daughter not to put it in the dishwasher, she put it in the dishwasher.  Both were fine...until they started the dreaded gray-streaking trick.  I did discover, however, that if you rub them down with vegetable oil, it takes care of the problem...for awhile anyway.  I just ordered my third flat beater and hopefully my last.  Hand-washing from here on out.
Please come out with a stainless steel version.  Thanks!