Microsoft has released a must-install patch for the Xbox One today that seeks to address a variety of problems with the new console.
The patch will have been automatically downloaded if you've opted for the power-using 'Instant On' (aka Stand-by mode) otherwise you'll have to download it yourself. The update deals with the following:
Addresses SmartGlass issues for some users when coming in and out of connected standby
Addresses multiplayer issues for some users when re-joining games
Addresses issues with inconsistent notifications for some users
Addresses dashboard performance for some users
Offers improvements for Xbox One’s TV, system update, and content update services for scaling over time
Updated wireless networking driver to improve connectivity issues for some users
We’ve got quite a few updates planned for the next year based on the community feedback we’ve been seeing, and I’ll have details on those in the future.
Source: Larry Hyrb