I did not take delivery of my TCH until April 18 and in southern Ontario there has barely been a frost since. However I paid close attention to the FE of my last car a Maxima SE 6 speed. Regardless of my best efforts FE was always hit hard on the morning commute during the winter. I did find that idling to warm everything up was definately not good for FE. Fire it up and drive immediately short shifting to prevent premature engine wear due to high revs.
Not only does idling burn a great deal of gas but fuel injection engines tend to flood fuel down the cylinder walls during cold idling and a worn engine is not FE.
I drove my first Camry this way, an 89 2.5 V6 and it was still not using oil between changes at 330,000 kilometres, that's when we parted company.
The fact my TCH will return less FE during the cold months does not bother me because it will still be better than a conventional vehicle.
Mine is a working car at 6 weeks old and already 6500 kilometres, results good or bad will show themselves quickly. Currently I am extremely pleased and would not trade if for anything (well maybe an IS F

) I'll keep you posted.