Agree with the view that you wouldn't buy one of these if economy was your #3 let alone #1 priority, but it's a real bonus for those days when you just want to cruise etc. I commute regularly between my home in Cardiff, soon to be Pembs to North Yorks where the company is based. The M4/5/42/1 A1 is not a place to bouncing off the limiter constantly, and given it's business mileage I don't want to out of pocket, so I'm probably going to set up the individual profile for super eco!
I've just had 18 months or so in a FL Octy II vRS 2.0 TSI, with a stage 1 Shark map. I never managed less than 28mpg in it, and that was cross country in attack mode; on a otorway cruise 70 - 80 ish I'd get 35-37 without trying. I've just picked up my
280 yesterday, drove it carefully from Cardiff to Pembs, got about 34, drove back at around 9pm and managed 29. Not brilliant, but acceptable, given I was driving it harder / faster than I realised.
One question, though and the obvious one - everyone using 99 (Tesco, V-Max etc etc) or are some of these in regular 95? I always used 99 wherever possible, occasionally 97 if that's all there was with the Octy, but then the remap was sensitive to such things, whereas the engine in factory tune wasn't significantly so.