Agreed on the general wonderfulness of heated screens but the bottom (reading) end of my varifocal glasses focuses nicely on the elements which can be irritating. I see about 6" to 9" deep worth of elements when not absolutely focusing well up the road. Really only notice when looking around at junctions et al but ...
Don't like to drive with fixed focus distance glasses as speedo and everything in the car is fuzzy.
Clive