I love these cross-trainers.  I have been wearing the 623's for years and for some reason never gave these a shot.  I wear orthotics which the 623's were a good solid base for.  I just got new and improved orthotics and the 623's weren't comfortable anymore.  I need cross-trainers for I do heavy aerobics and then they can also be used for walking so I decided to give the 608's a try.  I have fallen in love with these 608's.  The style and design is great but the comfort is truly unbelievable.  The fit is true to size and take my new orthotics perfectly and the whole combination then provides amazing support and comfort for my feet.  I am wearing in the new orthotics so a few hours a day I wear the 608's by themselves and the padding in them is superb.  They are so supportive, comfortable and honestly like walking on clouds.  The 623's were always ok for my orthotics but I was never comfortable wearing them with their own insoles.  I find the 608's far superior to the 623's and am beyond thrilled with everything about them.  Comfort, support, look.  Highly recommend.