At a little under two years in so far, testosterone has given me an extremely deep voice, tons of body hair (everywhere--chest, knuckles, stomach, legs, neck... etc), a large amount of muscle growth and... modest facial hair progress. I had a solid chinstrap with the most growth/density under my chin and Adam's apple and a semi-decent mustache with pretty much nothing below my lip or on the upper more visible areas of my chin and very, very sparse hairs on my cheeks.
To say I've been frustrated about that would be an understatement. At thirty, I don't really feel like waiting around forever for a quarter of the growth my peers are already sporting.
I started using minoxidil a little over three weeks ago and I've already noticed huge changes. The facial hair I did have has thickened up considerably and feels much more coarse to the touch. The patchy areas have started to fill in, I'm finally getting dark hair on the upper part of my chin and under my lip as well as on my cheeks. And, in general, I have loads more vellus hairs where it was totally smooth/bald before.
My plan is to stick with it for a year or so like most natal males with poor growth. Everything I've seen and read indicates that, once the hair goes terminal, it will not fall out once the usage of medication has ceased. This is not the case for hair on the head, though, which is why men using it for MPB have to continue indefinitely. If you stop taking it in the vellus hair stage (you see a bunch of blonde hairs popping up and just decide to let them grow on their own), they will most likely fall out.
One thing to keep in mind is this: It doesn't work for everyone. Some guys see stunning results, others see next to nothing.
For me, my frustration with progress and need for significant change outweighed my concerns over potential side-effects. Beyond that, it's pretty cheap and mindless to apply.
I had nothing to lose and everything (I've been dying for a beard since I was seven) to potentially gain.