I wore this shoes to the gym the same day they arrived.  I did not have to break them in.  They fit true to their size. I was very impressed how comfortable and light they felt.  I run 5 -5.5 miles 3-4 times a week.  I usually have knee pain after running.  These shoes made my knee pain go from a 7/10 post running to 2/10 on day one of wearing them.
Another great feature these shoes have is the breathability.  I have never felt air flow in any of my other sneakers.  These shoes keep your feet feeling cool throughout your running/workout time.
I would definitely recommend them to anyone who runs/exercises for their light weight, shock absorbance, and breathability.  I wear cotton socks with my shoes; so the breathability is a bonus for me.  These shoes are worth every penny.