I got Invisalign over 2 years ago to straighten both my upper and lower teeth(I am in my 30's and already had regular metal braces as a teen). To make a long story short, my top teeth were straight after 1.5 years of trays (keep in mind my teeth were pretty straight to begin with and only the front 4 really needed to be moved). My bottom teeth failed to straighten after over 2 years and a mid-course correction. I had to have metal braces put on my bottom teeth 6 weeks ago and they are already far straighter than Invisalign ever got them! My top teeth, even with continual retainer wear, are already shifting slightly. I feel that Invisalign is not worth the cost and does not move teeth as effectively as regular braces. The dental assistants at the office I go to seem to all agree. It isn't worth it.