These were my experiences with the following eyelash growth products:
Latisse - By prescription only, I bought mine from a plastic surgeons office for $120. It worked well, and my lashes were quite a bit longer as quick as one month later. The problem is that the area where I was applying it got dark, which made my eyes look like I had day-old eyeliner on all of the time. Not a good look for me. Also, the area right underneath my eye started to get dark, which made my dark circles look even worse. Taking all that into consideration, it just wasn't worth it for me to continue using Latisse.
After discontinuing Latisse, my lashes started to shed and they went back to their original state pretty quickly.
Revitalash - I can't recall exactly what I paid for this, but it was over $120 and it did absolutely nothing, other than irritate my eyes. I saw no difference after using for one month.
Urban Decay Lush Lash System - Love this! It works well, and at $42, it is much more reasonably priced than the Latisse and Revitalash options. No darkening of my eyelids, either.
I just applied every night prior to going to bed, and my lashes were longer, stronger, and thicker.