Forgot to link to this post from about a week ago which, among other things, mentions my belated first experiences with the XBox One.
1. Far and away the biggest thing the One brings to my house is a far, far more stable XBox Live connection than the 360 could ever manage. I know, if I really cared about online gaming I'd set up a wired connection to the router instead of using wifi (but it's a pain in the butt given the way things are set up in our house). But either the One's ability to use the 5 GHz channel instead of the 2.4 GHz one is making a huge difference, or it's something specific to the different implementations of XBox Live.
In any event, I installed Destiny on the thing, and not getting kicked off the servers every ten minutes makes Destiny vastly more addictive. The game is also prettier on the newer hardware; it plays at higher resolution with better textures, but it's a subtle enough difference that the superior networking is the real enhancement. I've actually been playing Destiny more than Halo 5, as lovely as Halo 5 is.
2. Halo 5 plays great but I do think the lack of splitscreen is unfortunate. To me, splitscreen multiplayer with your friend in the same room is a huge part of what I think of as the essence of Halo. Everyone's moving toward network multiplayer and making everyone buy a copy of the game. I suppose it's nice having the whole screen to yourself, but you lose something in face-to-face socialization.
I also have to confess that some of the single-player campaign's storytelling is kind of opaque and muddled to me, maybe because I haven't played through all the previous games' campaigns in order (I think I've gotten all of some of them in dribs and drabs, playing with friends). For a while I didn't even get that the POV was switching between Locke and Master Chief. But it's mostly an excuse for nicely-executed gun battles with space monsters anyway.
And it is by far the most visually gorgeous version of Halo. Halo 4 upped the graphical quality but also went to a dustier, more Call of Duty aesthetic. Halo 5 bucks the trend and brings back the chromes and blues of the earlier installments. Some of the landscapes are full of colorful flowers. It's nice.
I never could take seriously the way the grunts yammer in English like mischievous fantasy dwarves, though, and they brought that back too.
3. Turns out the Disney Infinity base peripheral is not inter-compatible between the XBox 360 and the XBox One, which is ridiculous, since it's just a USB device. That means I can't just buy the core download for the One and transfer everything else over. I think this is the end of the line for us with that clever but greed-motivated kids' game; we'll keep the 360 around for playing it.