I used Invisalign Express for a treatment of post-braces teeth. I had broken my retainer and had to wait to get a new one, so my teeth moved.
I love my treatment results, and I have experienced very few negatives (I am sure that it is because I only had to go through 8 trays, one button and had a spectacular orthodontist). I never have to be sad about my smile again. It was painful at times, but what else could you expect moving teeth to feel like? After only 4 months of minor inconvenience, my teeth are totally gorgeous.
I'm wearing my tray in the picture, so you can see how hard it is to see.
I would encourage everybody who needs mild correction to go for it, especially if your insurance pays for most or all of it! I can't believe I ever had reservations.