I'm about the most OCD of us all, I'm guessing, and my take on this, regarding the "hum" is...
I appreciate UPMan's honesty in explaining the situation to us. Knowing that I've mitigated it as much as possible (I believe this to be the case -- I spent hours experimenting with the fix), I'm fine with it. The reports of "zero" hum concerned me because mine isn't zero but now that I know, I bet most/all would consider mine "zero" under the same conditions they consider their hum to be zero. I am fairly confident now that my unit isn't an outlier or defective. For my money, I wanted my unit to be as perfect as the next person's for the same money.
In a room with a modest amount of ambient noise, it's fine. Like I've said, it's about like an old CRT hum or the SSD being written to on my fanless laptop -- and that's in a completely quiet room without the furnace in the basement or the refrigerator running in the kitchen the room over. When the refrigerator comes on ~20 feet away, I can't hear it at all.
I'm not worried about waiting 18 months for a POSSIBLE further minuscule reduction in operating noise because that's 18 months without this great scanner. I will be picking up my second unit way before then. It's really pretty much a non-issue for me as long as I know that all units are more or less equal after the fix has been properly applied.
In my current listening location, I don't even have the firmware noise muting fix toggled because it's that much of a non-issue. The only thing going in the room is a fan in a corner on low to keep the air from getting stale. I can't hear the operating noise ("hum") under these conditions.
My hearing is admittedly excellent. It's about equivalent to a teenager's still. I wish I could say the same about my eyes.
If *I* have gotten over it, I think anybody can. Don't let it keep you from getting the unit if you're interested and this issue is your main concern. If you buy it now, the fix should be applied and if it does still bother you, you can return it and wait for the next model or MAYBE a further miniscule reduction in noise way down the line. I bet the people who do will be few, though.