I upgraded and it all seems to have gone fine. I like the new browse and have used the edit feature a few times already. Having Windows 8.1 I already had a Microsoft account they had you set up so not a surprise.
I did see some people talk about having to pay for solitaire, etc. not sure why that is, on windows 8.1, you got them from Microsoft store, you have an xbox account for free and I still have access to all the same games I had prior to upgrade.
I like the tablet option and so much prefer the new multiscreen task option...the old 8.1 was very clunky and often I was on the desktop trying to get a calculator and wanting to pull my hair out so I'm certainly happier.
There is a driver issue I haven't figured out yet, I know there is still one showing windows 8 that I had an error on but it disappeared before I took notice and could write it down.