In the last period, some bikes are coming out with the chain return at the top to make the shock absorbing system work better (less pedal kickback). A high and forward pivot position will give the rear wheel path an upward and backward movement: this movement helps overcome large obstacles as well as contributing to pedaling efficiency.
The disadvantages can be less smoothness, however the chain return is felt, and an extra difficulty in keeping the rear stay short (which is why we find this shock absorbing scheme on bikes devoted to gravity). Most high pivot bikes use a link to guide the shock, allowing for control of the progression curve.
