That chip is more expensive than having a dedicated microcontroller that polls all of its GPIOs, performing software debouncing continually, and sends an interrupt on any change.
It's price is it's biggest drawback, but it is also replacing any electronics used to run the switches at 12 or 24v which gets you above the noise floor if you are operating next to something noisy like a VFD. from the 6818 data sheet: "Robust switch inputs handle ±25V levels and are ±15kV ESD-protected" [1]
