Upside: it truly does work, my lashes became thicker and grew so long that they brushed the inside of my glasses!
Downside: my lids (upper and lower) became quite dark after just two months of nearly daily use, my eyes would be bloodshot every morning after use, and it caused itchiness immediately after application. I decided to stop using Latisse for a couple of months to see if the lid darkening was reversible, which it was for the most part, but something interesting happened...I now have a small area where I have no lashes at all. I'm not greatly alarmed as another MD I see told me it is likely due to the normal growth cycle of my lashes and stopping the Latisse for a time signaled the lashes in that area to stop growing and they will return with or without use.
I am still undecided, 'cause the lashes ARE awesome and normal liner and shadow hide the darkening. One hint-> don't use the brushes supplied! A bottle last twice as long if you put a drop on your (clean) finger and apply it to each eyelid that way.