The shift points are adjusted in D and S, the redline is raised and (I think) the launch revs are increased too.
In terms of drivability, I would say it is different, not better or worse. In D the car won't shift so early and have you in 5th gear at 30mph or whatever. This helps with city driving, but i'd you've less options for "light right foot" fuel economy. I prefer the TCU tune over stock, because if you care about being in the highest gear for economy, you probably want a different car.
In M mode, shifts are quicker, particularly downshifts at 70mph+. You don't find that half-second "barp barp barp" lag before the next gear down engages. Upshifts on the limit feel a bit more savage.
On the ECU side I got map switching with stock/95ron/98ron so I can swap to stock if I want.
Really though, the lock-out sold me on APR. Car will start but won't move much without input of a code on the cruise control stalk. Until then the throttle pedal is disabled. In theory someone could drive it in 1st at crawling/idle speed somewhere but good luck with that.
