Let me start with myself:
- extremely poor 3rd party support (but then again I wouldn't rely on multiplats)
- some major 1st party games like Metroid still don't have their installments there
- lack of multiplayer component in a lot of games
- it isn't still priced reasonably enough
- Multimedia / Kinect / TV integration still needs some refinement, it's not all that it's cracked up to be
- Still lacks some essential system features from its last-gen counterpart
- Multiplats somewhat gimped due to lack of proper drivers and only recent introduction of improved development kits - worried about the long-term future in this aspect
- I'm very afraid about that MS support won't be as good in Poland where I live as it is in America and in the biggest European markets as in UK, France, Germany, Spain and Italy...
- I'm unsure if Microsoft will strike a deal with any of TV providers in my country and I'm afraid I will still not have an access to several nice features availble in America
- I'm afraid it will cost the same in my country as it did in UK on launch, despite being released a whole year after. That and I suspect they won't even provide a single game with the bundle.
- They haven't implemented Games with Gold on it yet.
- high power consumption on standby
- lack of Freeview integration (it's the HD TV free channels via DVBT after you just plugged it to a wall tv socket)
- having to have Xbox One powered on in order to use a cable box - seems not economic if you think of electricity bills, make it work on standby or hibernated or something, but not ALWAYS ON
- everything's behind a paywall
- certain stupid indie policies but they improved this
- not interested in any announced or hitherto released exclusives at all (as if: I'd rather get Wii U for its exclusives)
- Lack of essential system features to be found on PS3
- little variety among exclusives or console exclusives so far
- I'd appreciate more attempts at differentiating itself as a next-gen machine, apart from its raw processing power...different kinds of functionality would be welcome
- PSN is of inferior architecture to XBL
Actually, I don't mind lack of power in Wii U and some of its exclusives really interest me more than anything else on any other consoles, and whereas I listed a lot less points about PS4, they are a lot stronger reservations than this multitude of bullets I listed for Xbox One. But there, of course, isn't just "one system to rule them all" for me.
Everything has its pros and cons.
For the record, I - of course - don't own any of next-gen systems. But if YOU do, then do as you please - you can list them all, or you can list only those which you don't own yet.