Ok, so this isn't specifically an Xbox Live rant, but here goes:
Xbox needs full mouse and keyboard support, at least in the non-game parts of the UI. And I suppose I'd like to see Bluetooth support along with that, at least as an option for non-gaming audio and peripherals. The thing is, I use my Xbox One as a media device probably more than I do as a gaming machine. I like that I can use the Chatpad as a keyboard, and it's cool that I can plug wired headphones into the controller, but that controller is literally covered with buttons and triggers that can destroy my watching/listening experience with one errant touch. I still have a few HTPCs around my home, and I much prefer the way I can simply use any pair of Bluetooth headphones I want.
I'd also like to see improvements in Cortana-based voice commands throughout the UI. My nearby Alexa-powered Echo Dot puts the Cortana-powered Xbox voice commands to shame, both in terms of responsiveness and natural interactivity. At the very least, they need to come up with a way that saying "Hey Cortana" isn't required between literally. every. freaking. command. Also, they need to figure out a way to stagger Cortana-powered voice interactions across multiple devices. For instance, when I say, "Hey Cortana," within earshot of my Xbox, Windows phone, and PC, they all go into full-blown panic mode, and typically two of the three come back with "I'm sorry, I can't do this right now. Check back again after future updates." Ideally, one of those needs to tell the other two, "I got this." Maybe even a priority you can assign to devices. Something.
They absolutely must figure out a better way for families to share content. I don't think I really appreciated the importance of this until I had multiple Xboxes in my home. For instance, the Xbox in my living room is my home console, but when my kids want to play Overwatch against each other, then I have to log into the secondary console first and then switch to my son's profile, so he can play. This is because I own the actual license for the game. And if my Kinect happens to see me wandering back through the living room in the middle of a match, then it instantly logs me out upstairs and ruins the kids' match. Sure, I could buy separate licenses for each kid, but c'mon! While I appreciate the need to properly license and restrict content, there should be some kind of inclusive family licensing that balances the ability for a reasonable number of simultaneous instances to be run by anyone in the family.
There needs to be some way to guarantee input consistency for the soft keyboard/voice stuff. Some apps still use that weird, Xbox 360-era linear keyboard, while others like YouTube seem to roll their own entirely, which doesn't offer any kind of voice support. Either force app publishers to support the system-level keyboard, or provide some way of overriding it in apps that don't provide uniform support. If mobile apps aren't allowed to customize the input UI, then Xbox apps shouldn't be able to do it, either.
Come with a simpler way for me to buy games for my kids. I might like to give my son his own digital copy of Overwatch (see above rant), but as soon as the Store sees it's already installed on the console (albeit under my login), then it replaces the "Buy" link with "Launch." It doesn't even provide an option to purchase it again. Regardless, the few times I have actually purchased content for my kids under their profiles, it has required me awkwardly putting a set amount of money in their MSAs from my credit card, which they can then spend on the game. I should be able to buy a specific title for someone else, and then just give them a code for it.
I actually really like the parental control stuff, but it's too focused on me physically logging into the console to grant exceptions and extensions. My kids should be able to send a request, which I can pick up and respond to via my phone (either through the Xbox app or just a simple web form).