I waisay never felt it to be non-linear in the drop of the needle. Unless I fill the tank till it starts to over flow. I think when you fill the tank till it over flows, the sensor is somewhere deep inside the tank, and the fuel level is much higher (till the cap). While the car sips the fuel and brings the level down to the place where the computer think its 'full' you will see the needle is showing full.
And only when it goes beyond that point, you will see the needle drop. This I think is the result of 'non-linear' drop of the fuel gauge.
For me though, this never happens.. or may be I didn't notice it with that much keen?
By the way RedBull_ar, you said you have Civic too. Does Civic show 'fuel average?' in the dash? I was just curious..