Brief and to the point
It did. It's flatter (spring rates, dampers and roll bars) grippier, more agile and the extra 15hp brings added urgency above 5,000rpm. See the official press info here for graph-based evidence. This makes a car which can leave you a touch breathless in standard tune feel crazy fast.
I spent half of the first lap soaking up this information, but then Max pulled a large drift and I sort of did the same, and then I spent the next two laps behaving, depending on your outlook, like a man who didn't really understand why we were doing this, or a man told to do an entire lap sideways.
Here's a video of a nice chap called Graeme following me around Estoril. As well as being an occasional PH scribbler he's rather a handy driver.
BMW M6 COUPE
Engine: 4,395cc V8, twin-turbo, direct-injection
Transmission: 7-speed dual-clutch auto (M DCT), rear-wheel drive
Power (hp): 575@6,000rpm
Torque (lb ft): 501@1,500rpm
0-62mph: 4.1 sec
Top speed: 155mph (limited)
Weight: 1,925kg (EU, unladen)
MPG: 28.5mpg (NEDC combined)
Price: £100,680 (£94,180 for standard M6, Competition Pack £6,500)