I'm a 105 lb. casual runner, averaging 10-15 miles per week.  I've worn the New Balance 1123 for several years now and bought the 1540 because it's the "upgraded" version of the 1123.  The 1123 and 1540 have a similar fit and provide the same motion stability; however the 1540 is a much stiffer shoe through the sole.  I've had knee and foot pain from running in the 1540 that I never experienced with the 1123.  I want to like this shoe because the style is much more contemporary and the fit is snug, but the shoe is too uncomfortable to run in.  I now only walk in these shoes and run with a pair of Sauconys.  I'm disappointed New Balance no longer makes the 1123.