just to keep things simple and answer some of the questions here:
propecia is a great product, many people have success on it and the side effects are experienced by the minority, they often level off with continued use of propecia, and are completely reversible with the discontinuation of propecia. So is it worth the "risk" there is no risk, there is no permanent problems associated with this drug it is one of the safest ones out there.
NO you will not lose more hair if you quit, though you will lose pretty much all the hair you gained using propecia if you simply stop using it and any other hairloss product.
The graph is a good representation of how these products work, there is really no need to discuss it all that much further. almost 90 percent of people experience some degree of success (at the very least maintenance) on propecia, and results on this only improve with further proven additions to the regimen. If you want proof, check out the "success so far" thread in the hairloss discussions forum. these are only a few of the people that have had a positive experience with hairloss treatments.
get on a regimen now and stick with it!
