The Xbox One (if used as it was designed) is constantly on, so turning it on is instantaneous...you simply say "Xbox On" and it turns on, or you press the middle button on the controller. I have mine auto-signed into Xbox Live, so again, that is also instantaneous when the console powers on.
I don't use my Xbox One for Netflix (we have other items within the setup that do this) but all of the apps on the console work well and quickly. ESPN was especially quicker than the 360's version, and getting to streamed games was very fast...it seems to load online streaming content optimally so I would assume Netflix would be the same.
WiFi connectivity is much improved over the Xbox 360, and can now take advantage of 5Ghz channels (where as before it was isolated to only the 2.4Ghz channel). Speed of connection solely depends on your own network, so I can't tell you whether it will be fast or not because you may not have a good network. Mine is fast, but I didn't have speed problems with connectivity with my Xbox 360 either (I use Comcast for internet).
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