Sorry Mark I have to disagree: I used to have my HD350 set up as you recommend and I could clearly see some 'ghost' images particularly noticeable on end credits as I could see a light patch going the opposite way on the screen. When I moved the projector to level with the top of the screen the 'ghost' image went. I compared the sharpness at the screen and any difference went un-noticed to me, but back at my seat I could clearly see that the ghosting issue was resolved. It was apparent in certain dark scenes too if there was a bright area on a corner of the image, then an inverted similar sized patch would appear on the other (the Oppo screensaver was particularly noticeable, but actual video too).
Tough choice: Do I worry about a change in sharpness that I couldn't notice even close to the screen or something obviously wrong that I could see from my seated position?
I wasn't alone in seeing this effect, though it might have something to do with my very long throw. I haven't tried moving my X35 to centre to see if it does it, though I might just try it to see if it's something that they have improved since my oldHD350.
I do wonder if some of the issues of sharpness are due to tending to use short throw set ups in an attempt to maximise brightness? I would like to change my room around but I could only achieve the same screen size at maximum zoom in this new setup and I much prefer the long throw performance since I have enough light...