I've been wearing Ryka aerobic shoes for many years.  Typically I buy black shoes.  I loved the look of this black and white shoe.  And it's definitely comfortable, especially because I wear gel pads daily in my work out shoes.  However, it's not made for fast-moving step and CRT classes.  It doesn't feel stable enough.  It also doesn't seem to last very long: the shoes felt worn out after approx 5 months.