Well one down...

My wife's new laptop has done the transition from Windows 8.1 (which neither of us were keen on) to Windows 10 as it was available when I turned it on this evening. Took about 1/2 hour in all wile I watched a programme on Tv and it works fine.
*Old version of Office (2000) that is on it works fine.
*Two profiles on machine both transferred no problem
*Desktops have exactly the same icons they had before and backgrounds!
*Teamviewer works between machines
*Network in house works and all machines can still see each other
*No settings or fiddling with internet or anything - it justs works
*Chrome opens and favourites etc all there
*Passwords remembered etc for Yahoo mail etc
*No problem with wireless
*Boots quickly and shuts quickly
*My wife has never seen Windows 10 before and just got on and used the bits she needed as normal with no goggling or messing about
*Sound works

Haven't looked into Cortana or such because no real need yet.

Very painless and so far minimal disruption. And NOTHING like the hassle when she/we moved from Windows 7 to Windows 8.1