Just real quick, some erratic notes and thoughts...
I've had mine for only 6 hours now but so far it's awesome.
"Xbox, on" and like magic it turns on, as well as your TV and AVR. Sit down on the couch and you're automatically logged on with the Kinect camera.
"Xbox, go to Netflix" BAM! You're watching Netflix and you didn't even have to set down the sammich you wife made for you to find a controller/remote.
I have only played Forza 5 so far but it is awesome. I'm probably too biased to go into detail, I love the Forza series. I'd hate to talk about the negatives like less cars and tracks that they will inevitably sell as DLC. Being a Forza fanboy, though, I just throw them my wallet and say "take what you need". Hence the reason you should not base anything upon my opinion of the game.
After being used to the 360 for so many years, the new menus and how you navigate is quite confusing. I'm sure I will get used to it all.
It sure is a lot quieter than the 360 slim as well. I can very faintly hear something, if the room is dead quiet, from the couch.
The thing is big. I mean big.
If you don't have cable/dish, and you have a 360, there is no need to worry about the lack of backwards compatibility because you can plug the 360 into the Xbox One's HDMI in port. Instant backwards compatibility.
Currently, surround sound is not capable through optical out. Only HDMI. MS has released a statement saying this will be fixed soon.
There are some little things, such as the surround sound situation above, that are either not working or not included. Basically it boils down to because everyone complained about them going digital only, they only had a few months to rewrite the software once they backpedaled what they were going to be doing. <-- That typed out confusing, hope it makes sense. Everything will be fixed, improved, added, etc. in the near future.
Any specific questions I can answer?