I've got Win8Pro x86 running on my Acer netbook, Atom N270, 1.5GB RAM, 60GB 4200RPM HDD.
Booting from cold: abysmally slow - a lot slower than XP
Booting from hibernate: fast, about 15-20 seconds not counting BIOS startup
Hybrid sleep is disabled, it just flattens the battery. Boots to Desktop, none of that 'tile' rubbish.
And for some reason the WiFi glitches after a while, needing it to be turned off then back on - something that never happened under XP.
For what I use it for on the netbook, it's fine - but XP would do just as well, take up a lot less space, and run better because I wouldn't need a pagefile, (which I needed to turn on for Win8 to stop it complaining about lack of RAM).
I'll probably reinstall 'nlitened' XP on the netbook since its requirements are a lot less, and maybe give Win8 a go on my Desktop after 8.1 comes out.