Unfortunately, heredity has given me a very tiny jaw with large, Irish teeth. In an effort to minimize some of the problems, my parents (on the advice of multiple doctors) had all of my front baby teeth pulled out when I was about 7. This resulted in the unchecked decent of my top adult teeth, which eventually covered my bottom teeth completely. These upper front teeth descended so far that the gum line was no longer even; my back teeth erupted from one height, and the front teeth started significantly lower. In short, I had a ton of problems: crowding, a large overbite, and teeth that needed to be aligned in all directions. Luckily, I found a very skilled doctor.
I'm almost at the end of treatment and my teeth look so much better! I think they look even better than if I had normal braces, because Invisalign sometimes files the sides of the teeth to make them smaller. My teeth would not fit in my mouth without this feature (I still have one of my 12 year old molars half covered in gum because there isn't enough room for it to erupt. I'm 22.) Originally my treatment was scheduled to take about 1 year with 24 aligners. I wasn't very compliant, and zoomed through these in about 6 months. Aside from this being a fairly painful idea (if the trays do not fit well it really hurts, but if they do fit then pain is minimal) it did almost nothing for moving my front teeth up (closer to my nose). As others have noted, you can get away with wearing them a bit less, but this only works if you are not moving teeth up or down. Wearing them is especially fun after filing - teeth just about jump into place! It's wonderful, and any small gap created by the between-teeth filing is closed within a day. Brushing the aligners daily with toothpaste and a toothbrush keeps them clean and clear. Otherwise they get a bit yellow/gunky.
My lack of compliance lead to 2 more rounds of aligners (if you have the full Invisalign package - not the express or other paired down packages - you can get up to 3 rounds before having to pay extra) and my full treatment time is now 2 years instead of the original 1. I became more compliant with time and now I have finally managed to fix my overbite (yay!)
My teeth are worlds better, and everything from eating to smiling is much easier now. Also, since I had such a small jaw and terrible front arch, moving my teeth into place has changed my lower face for the better. I no longer have deep nasolabial lines and have a more attractive profile since my lower jaw has been able to move forward with the upper teeth out of the way. I used to really hate my nose, which I thought was too large, but I found that fixing my very weak chin really helped to balance my features and I have since learned to enjoy my face more.