Don't you trust the controlled clinical data with hundreds of participants over a relatively small group of men on here? There are success stories of course, but the most frequent posters have not stabilized their hair loss. That's why they're here so much- it's such a big issue that their brains must be working on it as often as possible, gathering every bit of information that could help.
The figures are that propecia increased hair counts in over 60% of men, noticibly for 42%, and maintained for 83%. It works best on the vertex (aka top of the head). I have a feeling that it maintains in that area beyond the 83%, and that people who lose more hair on it usually lose it up front. I believe the theory is that follicles in the front of the head are more senstivie to dht. Since propecia does not totally eradicate dht, frontal hair is the first to go for many. Though not all of course, many have diffuse baldness where the front is just the same as everywhere. Receders though have a hard time in the front with propecia.