I've tried 4 different laptops with various configurations. It always resuts in Nokia DLoad with the boot to WP7 following.
The people who have this working don't get the WP7 boot after disk mode which suggests that the bootloader of the phone is acting differently.
So it's entirely down to the bootloader the user has and nothing else as far as I can see.
Although, even with the same bootloader version two users are getting different outcomes so perhaps it also depends on the region of the firmware?
I'm out of ideas
By the way:
Diagnostics App Version: 188.8.131.52
Firmware Revision: ...12070 (I updated just now)
Radio HW Revision: 8255
OEM Device Name: RM-801 SE 615
Device HW Revision: 112.1402.2.3
Note: I have one of the first retail units. It was sent to me by Nokia before the public release.