Things haven't gone well with my tablet... I'm posting my experiences separately because, well, there's a lot more to say, plus I'm uncertain how much of my troubles are Windows 10, & how much are because of the hardware.
I wanted the update on the tablet most of all because it allowed store apps to be installed to the microSD card. Secondary to that, it runs the Home version of 10, so figured the update was unavoidable. I tried the standard update via Windows Update twice, & both times once I got to the sign-in screen, problems [crashes] only multiplied. I enabled the Insider program to see if I'd get the Insider version offered, but so far after a couple of days the new version of 10 has not been offered by or in Windows Update.
Microsoft is going to be releasing more builds of Windows 10. While the tablet I bought was a cheaper model/brand, it was nonetheless one of the more popular models/brands, so I'm fairly certain there was enough telemetry data sent back to Microsoft that they could know it was a problem. So there are several possibilities. One of those is that the 1511 upgrade may no longer be mandatory for the tablet, having failed twice. That would take care of at least one concern.
A couple of the installation methods I tried might be of use or interest, though ultimately they did not succeed.
I restored a disk image backup from the tablet to a VBox .vdi [Virtual Hard Disk], & fired it up in VBox as-is. It worked, & worked well enough that I was able to upgrade to 1511. Did a disk image backup of that, restored it to the tablet, fired it up, & proceeded to update drivers one by one. That also worked, but I had problems of Windows freezing or stalling when I opened the settings app that never went away. I also updated a graphics driver I shouldn't have, & couldn't get rid of it. In the future one of my 1st steps is going to be to make sure the boot menu is visible -- without one it was impossible to get into Safe Mode where I might have fixed at least that driver problem. At any rate, after a few hours it was plain this attempt was unworkable.
I also formatted the system partition on that .vdi with the restored tablet backup. You need a portion of the Windows 10 AIK to create a Windows 10 WinPE USB stick, ISO, or .vhd etc., so I added that to my Windows 10 Pro 32 bit VM, & make the .vhd [Microsoft format Virtual Hard Disk]. I shut that VM down, removed it's .vdi, adding the new WinPE.vhd + the .vdi from the tablet backup -- I also associated the 1511 ISO with its DVD drive. Starting this VM it booted to WinPE, which let me use Dism to copy the Windows 10 files from the ISO to the system partition of the tablet backup .vdi. Then I did another disk image backup, restoring that to the tablet's drive. That part worked, but again had problems when it got to the point where you sign in.
Using Dism that way is preferred by a lot of [particularly IT] folks. It skips a lot of time & disk space consuming parts of the setup routine, which just winds up using Dism anyway. And since it jumps to the point where setup has gotten all the files in place, but before anything is personalized to your hardware, the contents of the disk at that point should work with any hardware -- you can copy those contents however you want, e.g. backup & restore, & skip even more time &/or work, since you don't have to use Dism each time.
In an IT setting, or if you do enough installations to warrant it, you can maintain a .wim image of Windows setup files, complete with the latest updates & include some drivers, software etc. That speeds things up when you *apply* that image with Dism, since that's stuff that doesn't need to be done once Windows is set up & started.
Note that it's best from everything I've read to create a 32 bit WinPE in a 32 bit copy of Windows, though that may of course be wrong -- I haven't tried it in a 64 bit copy so I don't know. A 32 bit WinPE will work with 32 & 64 bit versions of Windows -- a 64 bit WinPE will only work with 64 bit Windows.
Note too that the WinPE you create with 10's AIK does not have a Windows GUI. When you create a WinPE disc/USB stick from AOMEI or Paragon apps for example, it has a GUI that runs on top of WinPE, but WinPE itself does not have one -- you get a screen with a blue background & a command prompt window.
Otherwise for the tablet I tried copying the files from a 1511 ISO to a USB stick, & using the Media Creation tool to create a setup USB stick, and tried running both from Windows 10, as well as booting to the USB sticks. All of those attempts failed/stalled.