I can give a first hand account on problems with Finasteride..
I was taking .25mg per day for a year. Yes, you read that correctly, I split the 1mg propecia tabs up into 1/4's after reading studies showing the efficacy was roughly 72% as effective as a full dose, but could help avoid sides.
I had a slight flare up with gyno, which really was only noticeable to me, but there was definitely an increase in glandular size, albeit a small one. Also, my sex drive was crushed. I literally had no urges to chase women, which was a complete 180 from my previous 28 years of existence.
My endo suggested I drop the propecia after a year of use to see how I feel, and low and behold two weeks later I'm horny as hell, and erections are stronger. It's now been roughly 6 weeks off and my hair is no worse for the wear using just minoxidil and ketoconazol shampoo.
Now I can say I have 3 friends who have used propecia with no issues what so ever, and they take the full dose. Everyone is different. I'm one of the people who got a negative response to it, but thankfully nothing permanent.
All that being said, I have 102 1mg propecia tabs straight from the pharmacy if someone wants to take the plunge anyway, lol.