Well, this is my first drive-by-wire throttle system so I'm not sure if there is any "lag" to improve upon, other than for people with quicker muscles than mine. The performance settings of the i-throttle can definitely let you produce a throttle signal that will seem to the ECU like someone mashing down harder and faster on the pedal, so it can make the car feel more powerful and maybe even let someone who can't push the pedal fast enough get off the line more quickly.
The ECO settings greatly improve the driveability of the RAV for me. After driving it around in snow and ice for a couple of days, and on the highway for a few hours, I can say it does exactly what it claims. In the max ECO setting the car eases off the line smoothly with no effort to control pedal pressure at all, then as one steps through the settings the throttle curve becomes steeper and the zip off the line returns. Full throttle is still always full. The performance modes make the throttle response more like what I would have preferred 30 years ago.
The unit seems quite well made, and there are a lot of them around in Camrys and Accords, so I am reasonably confident it will not cause catastrophic problems. There is a wire to connect to the brake lamp circuit to shut down the throttle output if something goes awry. I tested my car without that wire connected and with the i-throttle working; if i floor the gas pedal and hit the brake the ECU still cuts off the throttle. I am much more concerned that my weather-tech mats will tear out of the hooks and climb up over the pedal myself.
The control head is compact and will mount almost anywhere. I chose to whittle down the case so it would fit in the coin tray on my car. Setup takes a few seconds and the whole system is plug and play on our cars.
The mode can be changed on the fly or stopped. When the car is shut off it will revert to the normal mode, then return to the last mode used if desired, with a single button push. On the road it alternates display between the mode and the throttle %. All in all I rate it