Stationary Bouncers...not the seated ones?

My son is 12 weeks old...can hold head up really well, wondering if he is too young for one of the stationary bouncy/exersaucers? He has almost out grown his bouncy seat and needs some sort of activity. Also wondering if these are bad for a child...I heard the the walkers caused bow leggedness and spinal problems if used too soon. Do these cause the same problems? Or are they just a waste of 80 dollars??