I guess your "random hardware" was still not random enough: My notebook that goes crazy after the upgrade is certainly not an "oddball" as it has

the Intel processor,

the Intel chipset,

the Intel graphics card,

the Intel WiFi card, most expensive of that times,

the maximum amount of memory for the CPU and chipset (4 GB) and

the most expensive Windows 7 version installed.

I'd even say it can't be more straightforward than that. And what's worse, the Windows 10 Upgrade program "tested" the configuration and claimed "everything will be fine." Now it nags even after I reverted to Windows 7. Windows 7 has no problems, Windows 10 has problem with interrupts handling.

And the Windows 7 "hours long" update problem is surely known to Microsoft, I've diagnosed it on my machine too, this function:

    wuaueng.dll!CUpdatesToPruneList::AddSupersedenceInfoIfNeeded

appears to still (after the 2016 March update of the Update Client (7.6.7601.19161) and KB3102810 installed) be called almost infinite number of times. I guess it's some unnecessary recursion on an O(N to a high power) loop which was tolerable for small number of existing files in the list of all updates, and now explodes. Microsoft appears to avoid fixing that code even if it's quite obvious for anybody who knows to interpret the stack.