Hi guys,
I've been on Propecia for five and a half years. After a week or so of use, I too noticed a marked decrease in libido. I'm not saying I couldn't get it up, just that I was not nearly as horny as I was prior to starting Propecia. Also, my "loads" were much smaller than before. However, since the drug worked well and stopped my hairloss, I was willing to keep using it and sacrifice some horniness. I'd rather be less horny and have hair, than be a bald old horny pervert who can't get laid (heh heh)
I'd say that after about a year of use, my libido started to return to normal. Five years later, it is about how it used to be, but my "loads" are still smaller than pre-Propecia, although it still feels just the same.
All in all, I'm happy with Propecia -- it's the only thing that really works for me.