I opted for this, so far i have done around 7000 miles from motorway cruising, town driving, lots of stop start traffic and fuel economy is around 18 - 26 mph, this is slightly better than it but now i have around 700bhp, I decided to have the 3.26 final drive ratio and i am geared to around 190mph, the 2.9 drive ratio should be more economical though.
Daily use is just perfect and there is a gearbox setting (drive logic) to suit pretty much any mood you are in ranging from the relaxed D1 to the aggressive shifting D5, flick the gear level or use the paddles and go into manual/sequential mode and use S6...the only word i can use to describe it is "Mental".
Gear changes are super smooth, most of the time you only know it's changing gear because of a change in engine tone and the noise it makes with the throttle blipping and rev matching on down shifts, also shifting on full boost with no loss of boost and constant power delivery
Was it worth it, trying to not be biased honest, but yes definitely worth it. If you already have the Syvecs then it's not much more of a jump, if the gearbox ever decided it had had enough then these can be picked up for a few hundred quid.