I don't know what the percentage of people affected is, but I suffered nearly complete loss of libido that crept up on me and took a couple of months to return

I don't know what the percentage of people affected is, but I suffered nearly complete loss of libido that crept up on me and took a couple of months to return after ~1 year on propecia. I don't think I've gone a full month in my life without even having morning wood before or since (and that wasn't a high-stress time in my life or anything).