Actually, it was Windows 7 that surprised me positively, when we tried to install it on an 2004 PC with Sempron 2800+, 512 MB RAM and SiS integrated graphics. It was really snappy, worked as quick as XP SP1. As for Windows 10 - well, I'm hoping they'll improve it further - my TPR lasted only 18 hours, after which I simply rolled back to Win 7 x64 I had. Windows 8 was schizophrenic - didn't quite know what it was, it was forcibly dumbed down plus, many functions were doubled between standard Control Panel applets or MMC and the "apps". Window 8.1 was still dual-personality, but you finally got to say, which personality you like more. Windows 10 is just evolution of that - it's still in a very raw state, unpolished, and missing things I actually like in previous releases.
DECpc AXP/150, Sun IPX, Ultra 60 (broken), Mac 630, G4 Digital Audio, Amiga 1200T, IBM 7009-C10, HP Envizex a, A180, B132L, C360, C3600.