I also wear with Terramar Micromesh boxers under my cycling shorts and have never had any saddle sore issues. They fit tightly and have a lifetime antimicrobial treatment. Here's a link for those who may be interested:Camilo said:I agree with this.
If you do want to wear underwear, find some wicking products w/o seams in the crotch. I have a few pair of Terramar Micromesh briefs which work well, but there are similar other brands. I have ridden in them under cycling shorts and they don't bother me. I do prefer no underwear though.
http://www.campmor.com/webapp/wcs/stores/servlet/ProductDisplay?&productId=39286194