Everyone that has a I-Shock loves them... They are a good shock and well priced, there are better shocks than i-shock of course but they in the $500-$600 mark.
You could goto a thumpstar dealer and get there i-shock copy its in the $80-$100 mark, my mate has one and likes it but its not the smoothest shock either but its stronger and has a heavy'r spring than the standard shock that come on his bike.