Rogain really does grow hair... The only thing to understand is that is grows hair in places that your body cannot, meaning you have to use it forever if you want "permanent" hair replacement. All hair grown with Rogaine or any other drug will typically begin to fall out after about 10 days of non-use. Your body is the only thing that can really grow hair.
What happens... Your (healthy) folicles can support up to 10 single strands of hair... as time goes on your follicle gets "gunked up" with various products or in males especially (DHT) dihydrotestosterone, making it harder to grow hair.
Imagine an empty glass (which is your follicle)... the bottom of the glass (follicle) is where your hair strands get their "food"... now imagine putting cement in the bottom of the glass, restricting your hair's access to it's supply of food... your hair then takes "shallow" root and you start to get little almost fuzzy pieces of hair and instead of 10 strands of hair, you might have 2 or 3. Eventually, your hair cannot break though the build-up and your follicle will die. When a follicle dies, there is no way to repair it and your scalp becomes smooth and shiny.
There is a product called Nioxin which is designed to help your hair get the "food" it needs. It does not grow hair. It cleans out your follicle to allow new hair to grow. When you first use it you will lose some hair, but know that it is the hair that is planted in the "shallow" part of your follicle that you are losing. After it has cleaned the follicle, new hair will begin to grow. You do not have to use this product for the rest of your life. But, if you do not take care of the follicles, they will most certianly get "gunked up" again.
I have been using this product for 3 years now, and I have noticed a significant difference in the volume of my hair. It took a good year to really see a difference (beacuse my hair was growing naturally and that takes time), but I love it! You have to use the system, not just one product so it really is an investment but for me it was a no brainer, I would have paid anything for my hair to stop falling out...
I know I can never get back the use of the follicles that have died, but I know that if I continue to use the product, I will not lose any more hair...
Sorry this is so long... good luck!