Coming from PC / Nintendo user to Xbox for the first time:
Graphics are sub-par already. This should be the peak of graphics for XB1, it's not as if the hardware is magically going to upgrade over time whereas with PC it will. GTA 5 is a prime example of a vast difference in graphics.
Originality is lacking. Froza Horizon 2 being the exception, when I played literally every other game including 'glorious' Destiny that's supposed to be one of the most expensive games ever made - I was deeply disappointed. The best Xbox One has to offer with games vs PC is a joke with the exception of Horizon 2 which I love.
Games are easier to play on PC than Xbox One. For example, Assassins Creed - I never had the difficulty of jumping on things I didn't attend to or aiming. Same with Battlefield Hardline, my accuracy with a mouse is far superior than a joystick even after 30 hours of binge playing on XB1.
Media compared to Roku sucks. Part of the appeal for me going from PC to XB1 was the fact I was told it was an entire media entertainment experience. Frankly Roku has more apps/channels and is faster even when no games are playing on XB1. That's nuts.
Kinect is what pisses me off. It has so much potential yet the majority of people end up only using it for voice commands. At first I played the kinect exclusive games but it's one of those things where it's a fun starter but I never stuck with it because it wasn't engaging enough.
Updates Microsoft gives out are little increments here and there and they always make it so 'glorious' that they're finally doing some that was asked for 12 months ago.
Gold Live is a money grab. On PC I never have to pay for Multiplayer as an extra. That's how it should be with console as well. If I play an MMO, they have dedicated servers just like XB1. It's part of what I'm paying for and the MMO's I play don't have monthly subscriptions, it's a one time deal just like XB1 games yet Microsoft constantly says "well then you'd be stuck with unreliable public servers." That's only if you are so cheap that you feel inclined to do that. Again, many PC games have dedicated servers without any extra charges.
Do I regret buying an Xbox One? No.
Would I recommend my PC gaming friends to buy one? No.
TL;DR: You hear about "oh PC is so great" bla bla bla.. well, it is and I think XB1 could match a lot of what makes PC great by dropping things such as Gold Live and encouraging more developers to be a lot more creative. No regrets buying it, I just get annoyed how tiny upgrades are over glorified and the lack of creativity found in games and the system itself.