I'm changing to tray 3 today, and my treatment is going great so far. I have a mild case and need 9 sets of aligners in total. So far with tray 2 finished, i have definitely noticed movements of my teeth.I had 2 spaces filed between my bottom teeth, but it's really not that noticeable, especially when you have your trays on. Other than this, I personally see a benefit in frequent brushing which, if you do regularly, should not give you any cavities. Cavities occur when you don't check your teeth prior to the treatment and cavities develop if you don't brush AND floss your teeth. This is something you have to consider.
I've read that people complain about dry mouth and chapped lips during the treatment. Well, any treatment comes with some inconveniences, and it's something extra that you have to do: use moisturizing lip balm when you go to sleep, and your lips won't get chapped during the day. Drink lots of water, which is actually healthy for you.
It seems like many people expect that, considering higher price for Invisalign, the treatment that they offer has to be %100 painless and comfortable.This is never the case,there isn't such thing as painless and enjoyable treatment. Also, the more difficult your case is, the more complications your treatment can face.The more trays you have to wear, the longer it will take for you to see the results. On average, each tray moves your teeth up to quarter millimeter, but it's hard to tell which teeth are moving and by how much with every new tray. Complicated cases might need additional refinements, but it's the same with the traditional braces, except that the later give you more problems with cleaning, breath smell and blisters on your cheeks and gums.
A lot in your treatment also depends on the orthodontist, so don't rush to blame it on Invisalign. Invisalign is a computer based treatment, but your orthodontist is responsible for making correct impressions and approving your invisalign treatment. Without ortho's approval, Invisalign won't process your trays.
It's your call to make, but I don't have regrets so far with my treatment. With my case of teeth, i think i found optimal treatment and I'm looking forward to see final results