I have only worn them a few hours, but already know I will love them.  The arch support is great.  It is recommended that you go slowly with wearing them the first few times and it is clear that if you have been wearing sandals with less support, like I have, it is necessary for a break-in period.  Note: I ordered one size down on the recommendation of others and I am glad I did.  I have a wider foot and I was concerned it would be a problem, but it is not.