I'm now on my third Jazz, having started with a 2010 I-shift, followed by a 2013 CVT and now a 2016 CVT.
Yesterday I did my usual trip from the West Midlands up to North Lincolnshire, a round trip of 250 miles of mostly motorway driving.
Going up there, keeping the speed to 60mph max, the readout showed 68.2mpg and the return was 58.6mpg, which was down to a headwind. Even allowing for the optimistic readout, I guess the average must be around 60mpg, which I am more than happy with.
I guess those that comment about the Ivtec lack of guts at low revs, are mostly driving a manual gearbox car.
With the CVT, the situation does not arise, you simply plant your right foot, the revs rise and you Go!
Certainly for me, I have not found the performance to be lacking in any way.