I have just stumbled across an absolutely AMAZING thing about Windows 10, so I thought I would share my experience.
 
I recently went ahead and just beat the deadline to upgrade to Windows 10 for free, for my primary desktop computer, and all went incredibly smoothly, in an upgrade in-place.  No problem there.
 
I had been hoping Windows 10 would deal with a memory issue I had been having with my Windows 8.1 install on that computer, where I had 32 GB of memory, but the BIOS kept a little over 17 GB as Hardware Reserved, and no changes I tried would alter that.  Once in a while, it would boot up and 30 GB would be available, but most times, only 16.7 would be available, with the other half set to Hardware Reserved.
 
Soooooo, after 2 hours of diagnostics at the computer shop, we determined it to either be an issue with the CPU or with the motherboard.  (it could have been incompatible memory as well, but we swapped out several other memory brands to no avail).
 
I was offered the opportunity to swap out the motherboard for one from another manufacturer, and I took it, however this would mean I would have to reinstall Windows, and all programs and plugins, because it would detect the different motherboard serial number and all that, as well as the drivers being all different, etc.  Normally, this would take me about a WEEK of lost time, to install Windows, apply maintenance, install programs, configure everything, and move libraries and such around, etc....
 
SOOOO - tonight I installed the new motherboard, got all the devices plugged in, memory installed, CPU seated, and fired it up, fully expecting to be dealing at the BIOS level until I could get Windows installed, and all the subsequent installs done, etc.
 
Instead, my computer went ahead and booted all the way to Windows, adjusting for the new devices along the way, and it booted all the way to my regular account screen, with all of my background images and settings all ready to go.
 
Incredibly, Windows 10 has been built SMART enough to deal with the rather brutal process of dealing with all the fundamental changes associated with using a completely new motherboard.  All I had to do is reactivate Windows and Office, and boom - all done, from what I can see thus far.
 
This has saved me LITERALLY about 2 WEEKS of downtime, that I was fully expecting to have to wade into this evening.
 
Instead, I am about to continue work on a Sonar project I am working on.
 
How kewl is THAT!!!!!?????
 
Bob Bone
 

Very nice

That was one of the big upgrades in 10 for us IT folks is a new Hardware Abstraction Layer. MS last made a big improvement in Vista, but now they've got it to a really solid state. They are actually looking at phasing out sysprep as a result of it not being needed. The only thing I know for sure it can't handle is changing from a UEFI boot to a BIOS boot and that has to do with disk format, no way to change that. Also it might not work if you change the interface type of the boot disk, but I'm not sure it may be able to handle even that.
 
Either way, for 99.99% of things it is hardware agnostic now. Switch the hardware, it'll deal with it. One of a number of nice system level improvements to the OS. The flashy user facing stuff is always what gets the publicity, but MS usually puts in a lot of work under the hood in new OSes.

Very good to know and good for you Bob on the seamless MOBO replacement......that IS excellent news. 

YUP!  I am already back to working on music projects, where I HAD thought I would be mired down in starting from SCRATCH with having to reload the world.
 
WAHOO!
 
Bob Bone
 

With 30 or 17GB of memory?

@Bapu - sorry if I wasn't clearer. :)
 
I had a situation where with 32 GB of memory installed, the computer would acknowledge that 32 GB was installed (in System Information). BUT that only about HALF of that was available.  The BIOS and/or Windows 8.1 flagged about 16-17 GB of memory as "Hardware Reserved".  Memory all checked out fine, swapping memory out didn't work, and none of the web-suggested notions worked either.
 
So, long story short, I swapped the motherboard out for one from another manufacturer, and the issue vanished instantly, and I have about 30.5 GB available.  
 
And, in addition to the memory issue vanishing, I discovered, with GREAT happiness, that Windows 10 is FINALLY smart enough to adjust things internally, when something as profound as a motherboard swap has occurred.  It posted a message about adjusting drivers, and completely handled it - booting up to the new motherboard with no action on my part needed, other than my resetting a handful of registrations (Arturia, Native Instruments, EastWest, Microsoft Office).
 
Bob Bone
 

Good to know that going forward it will most likely never be necessary to do a clean install due to a hardware upgrade!!! 
 
Just spent the past two weeks with a last minute free upgrade to Windows 10.  Had to do an upgrade in place with Win 7 Pro 32-bit to capture the free upgrade, then using the Windows 10 Media Creation Tool I downloaded and clean installed the 64 bit version.  All good now, but like you mentioned, a clean install is a productivity killer for sure!!!
 
Microsoft has released some info that re-activating Windows 10 after a motherboard change will also be easier.
 
https://support.microsoft...-after-hardware-change

Good to hear as I have a rather old motherboard now.