So picked the M3 up from welly in the weekend, love it. Got a bit to learn in terms getting a feel for it and setting it up the way I like, with various adjustments available around the dct, throttle response and edc etc. One thing for sure, it doesn't give the thump in the back the way a tuned 335i does. No doubt she goes hard when the revs are up, but you can understand why BMW may have deliberately kept the boost pretty low on the n54, so as not to sabotage the s65.
Re gas mileage, here is what it looked like about 260kms into my trip from BP Mana, near Porirua, to New Plymouth. I haven't been able to verify this with a refill, but even if it's 20 or 30% optimistic, I'm more than happy with it. It crept up to 10.1 litres per 100kms by the time I got home, as the roads got more entertaining and I took a wee detour through some twisty bits ?