I was a Propecia user for 15 years. Before trying to conceive, I decided to do a sperm test, and had a result very similar to one of the earlier posters:
-Progressive: 0%
-Non-progressive: 10%
-Immotile: 90%
-Motility: 10%
-Count/ml: 40 million
-Asthenozoospermia
I consulted the doctor at the fertility clinic, and he said for sure it's due to Propecia, so stop taking it and come back in a month and a half.
Well, I did as he recommended, and the second result was as follows:
-Progressive: 45%
-Non-progressive: 21%
-Immotile: 33%
-Motility: 66%
-Count/ml: 48 million
-Normal
So sure enough, it was the effect of the Finasteride, which quickly went away after discontinuing the drug. I must add that there was no visible effect on the sperm, nor any libido effects that I noticed during the time I was taking it aside from the normal effects of aging.