"it should be a completely sucessful and flawless update"
Yup, just like SatNad told us that Windows 10 was a successful launch.
Personally, I think it's going to be an enormous cock-up. Hundreds of thousands of XBones all downloading and installing and updating at more or less the same time, what could possibly go wrong ?
Hint : ask any company how a major launch went on Day 1. There are more examples than I care to list.