5+ years on dutasteride .5mg. I have to admit I haven't needed to worry about my hair since; however, recently I have been experiencing increased shedding. During this period of usage I noticed significant regrowth and felt very good about the way my hair looks. I even noticed significant regrowth around my hairline. I had previously had very little success with Propecia/finasteride.
I will say that the side-effects can be noticeable. One swollen/enlarged breast (but nothing that exercise and diet can't fix), tenderness of the skin, and ... whether it's related or not ... premature gray hair.