I like the dry ice method but I am not sure what I am going to do with the leftover two pounds of dry ice! I wash both by hand so that I do not have any detergent residue. There are some special cleaning agents just for crystal that have worked well for me. The one I am currently using is Stem Shine which is/was fronted by the Wine Enthusiast magazine. I found the stuff at my local wine shop. It has worked well but the stains will still come back with use.
I was given a micro fibre tea towel for Christmas which was designed specifically to shine crystal wine glasses. It seems to work extremely well, so since then I have hand-washed all my wine glasses.