As seems to be the case with several others on this list this year has been a bad fireblight year for me. I planted most of my apples and pears and Asian pears in the fall of 2007. Last year I had several little spots of fireblight on my Kieffer pear and then my Comice pear got some fireblight and despite my efforts to keep it pruned out it quickly spread and killed the whole tree. None of my other trees had any fireblight last year. This year all my pears (Euro and Asian) had fireblight. I had to prune my Moonglow back to a 3' tall stump with just a couple lower branches. It had the worst fireblight. It might be significant, however, that a cow got loose and broke the top out of my Moonglow a couple years ago, so there was lots of vigorous, younger growth on the Moonglow. The Kieffer had extensive fireblight damage this year. I had to prune out major scaffolds. It looks terrible now post-pruning, but there's more left than with the Moonglow. My Asian pears, two Korean Giants and three Shinkos, all took much less damage than my two remaining European pears (not counting several younger trees, none of which showed any problems) and should even produce some fruit this year. The Korean Giants might have taken a little more damage than the Shinkos, but none was really bad. With my apples I had no fireblight on my Gold Rush, Arkansas Black, Liberty, or Golden Delicious. The worst fireblight was on my Enterprise, then not quite as bad on the Stayman, and then pretty minor on the Brushy Mountain Limbertwig. This is the first year I've seen any fireblight on my apples. Another observation was that I seemed to have more fireblight on the limbs just past the sticks that I used to spread branches for better angles. It looks like the pressure against the bark cut off the flow of sap or something like that and that the limbs just past those points suffered for it.
My pears are mostly on the west side of my barn, so they're shaded by the barn for the first couple hours of the day. I wonder if good morning sun (maybe even exaggerated by an east-facing slope) would help to dry the dew off sooner and if that wouldn't reduce fireblight pressure.
I'd be interested in hearing about others' observations of relative fireblight susceptibility in unsprayed pears/Asian pears.