I just got a cheap cheap 8 inch tablet that was sold off for 50 EUR (about 55$) (with a small bluetooth keyboard included and a 1 year subscription to Office 365 that can be use in one computer only, but not necessarily the tablet). Of course the specs are low: 1Gb of RAM, 16Gb of "hard disk" space, atom processor. The tablet came with Windows 8.1 32 bits. I had upgraded it to Windows 10. But, beside from the fact that the gravity sensor don't work (but should be fixable with a third part driver), the overall experience was not good. Everything feel sluggish, much more that in with Windows 8.1. particularly the menu animation. I wonder what's the real minimum hardware specs needed to run Windows 10? I have the feeling that you need more than with Windows 8.1 and more than the minimum announced by Microsoft? Something that tends to support my idea is that current native Windows 10 tablet are generally more powerful than that. I do not see these ultracheap tablets with Windows 10 anymore.

I had the good idea to create a recovery USB key from Windows 8.1 and I used it to factory reset my tablet to Windows 8.1. At least Windows 10 having been activated, I think I can now upgrade even after 29 July (Microsoft says that you can indefinitely reinstall Windows 10 if you have installed it before 29 July).