At 46 years old I was bequeathed some money and decided to spend some on getting my teeth improved (something I'd always wanted but couldn't previously afford). Invisalign was offered to me as an alternative to what I'd asked for.
After the initial consultation, impressions, x-rays, etc., my provider (not an orthodontist, but a dentist) said that Invisalign thought the case was too complex but that he had talked them round. I suppose this should have made me cautious. Invisalign seems like a brilliant system, and they tell you it's invisible once in. And compared to traditional braces, of course, it is.
I started in April '09 and I was delighted with it both from a comfort and visibility point of view up until I went for a check up about 2 months in and was told I needed a mid-course correction (another £300). Then, they weren't so invisible because I had 10 (yes, TEN) buttons on my teeth, four of them on the front two teeth top and bottom. Trust me, it's pretty visible now.
One year on, and six months into that mid-course correction (which took a LONG time to finalise and kept me in a 'holding' position for months) I've now been told that we have to abandon Invisalign and go for traditional braces. Great. Metal braces at 48. And I can't NOT do that, as my teeth look worse now than they did when I started, with gaps where the teeth have been filed down, and where a tooth has been extracted.
If your teeth need significant rotations as mine did, DON'T, DON'T, DON'T go for Invisalign. It's been a huge waste of money and TIME for me, and I very much regret starting it.