I think I only have one PC running windows 7 and the reason is video performance, the GMA 3100 is very bad on windows 10 with high CPU usage by DWM, while on 7 it's lower with Aero and non existent with it turned off, other that that I don't really see a reason to stick with 7 for so long,
for this PC I'll try using it like it is on 10, the CPU is a quad core so it doesn't completely kill performance I guess, but if it gets too annoying I'll add some video card.
but, I never had any problems with XP or 98 just doing basic things online, I wouldn't want to use 7 for sensitive stuff, but for gaming I wouldn't worry too much, apart from driver support and games support in general,
windows 10 can be annoying but it's windows, I just use a offline account, disable most of the default options (shutup10 is helpful), remove the "apps" from my start menu, never touch the cortana thing, uninstall onedrive, and it feels fine...
thee are lots of silly things like defaulting to some "App" style settings when it's much easier to solve on the old interface, but oh well, you can still mostly find the old interface.