I am 28 years old. When I was young my parents could not afford braces and now that I am older I have wanted straighter teeth buy did not want metal braces. I finally decided to go with invisalign. I can't believe I hesitated so long and did not do it sooner.
They are not completely clear but they are very subtle and you feel comfortable smiling without a mouth of metal braces. Also, when you switch retainers they hurt the first day or two but then you get used to it. As far as cost, my ortho got my insurace to cover some of the cost and then I paid the rest of it off in installment plans.
As far as does it work. My mouth feels so much better and you can really see my teeth straighter. In my case I feel it has worked however you want to make sure your teeth are not too bad because they only work for minor cases. I had major overcrowding on my bottom teeth and I did not think they would work but they did. I would highly recommend this product for adults.