<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Efrem:
It's a good loss-free way to get miles from AA (or UA) to BA, if you want to do that, but you don't come out ahead.</font>
You definitely don't come out ahead. If Diners Club does the BA promotion again this summer, you will get the same number of BA miles as you had AA or UA miles. However, with BA's new program dilution, premium awards on BA cost much more in terms of miles than before. See the BA board for details.