Win 8.1 x64 Update 1 from 7
Had 7 x64 for while. Waited nearly year to go 8 & 8.1 and happy enough with move. Seems to use extra ram fine under x64, less crashes (none lately), fast boot.
Main barf might be that IE 11 hard wired in. Some sites aren't configured for it yet and won't load but main ones ok. Sometimes the videos at those problem sites failed to run but finding they finally do. Install Chrome just for the ones that may need a specific loading.
No idea what they'll do under Up 2 when released. Right now can boot straight to desktop like before. Things like Skype run well as do some of the non desktop things. I'd go for it with a little time set aside for learn curve.
Have decent ram, cpu, maybe a large second drive or good size SSD main drive. Their Outlook.com & onedrive are good and all the tools like Lastpass work right. g/l