Lamborghinis of past have gone through several refresh cycles - Countach LP400 to Countach LP400S, LP500 and LP5000, Diablo to Diablo SE, VT, GT, VT6.0 and the list goes on for Murcielago.
Each refresh cycle usually added more engine displacement and power. Everyone knows that horsepower is what sells sportscars and in 2017 it takes more than 700 of those four-legged farm animals to impress the modern supercar buyer.
Aventador is already 5 years old and auto industry, unlike Silicon Vally, actually has progressed since 2011. Performance in V8 and V10 "junior supercar" segment is so high, that Aventador, with all its 6500 cubic centimeter 12 cylinder might, can't keep up - even to it's own little brother Huracan.
To remedy this, Lamborghini managed to extract additional 40 metric horsepower from the 6.5 via upgraded valve-train, and add some obligatory styling changes for a full mid-life refresh.
Applying different "skin" on same body can often lead to awkward results (Veneno), but not in this case - Aventador S doesn't look any worse than Aventador from 2011.
The power, which now is at 740 PS, should be enough to keep the lesser-engined stable mate Huracan at bay, if not defend against those pesky turbocharged 8 cylinders - Ferrari 488 GTB and McLaren 675.