I have worn Boston Birkenstocks for many years.  A new dress code at work made it necessary to purchase shoes with backs on them.  I toyed with buying Londons but after seeing Alpros at my national congress, I decided to try them.  The expense is very worth it.  At Congress (nursing) they said to size down.  I did not.  I have always worn a 39 and that's what I ordered.  I am very happy with that.  The high backs are not noticeable.  The velcro straps are much better than buckles.  The covered cork is the best as I work in an OR.  I am on my feet for 40-60 hours per week.  Other than the first day, I have not had a bit of awareness of having shoes on.  First day, they felt stiff.  I understand it takes walking to form them to your feet.  It only took the first day.