There's a lot of slop when you've just got a speedometer and your ears for feedback. With an SG or UG, you'll find that you tend to get a lot deeper into the throttle than you have to be. "Instant feedback" isn't just some mantra they're repeating here, it's the most valuable single "technique."
I really liked Torque. Anything your car has a sensor for can be displayed any way you want in a really good looking package. I used it for less than three months, though, because a dedicated display is better than swapping your phone in and out all the time.