Please note that while this voids the Xbox One's warranty, YouTube user 'Brian Williams' has posted a new video claiming that replacing the console's 500 GB hard drive with a larger capacity one will make the system run incrementally faster. You can watch the video below.
DO SO AT YOUR OWN RISK!!
WIlliams replaces the Xbox One HDD with a 500GB Samsung EVO SSD and a Seagate 1TB hybrid SSHD, and proceeds to demonstrate a 20% faster load time for Call of Duty: Ghosts, and a 10% faster boot time to the Xbox One home screen. We haven't yet tested this ourselves, so can't verify the claim.
If you're tempted to do this, keep in mind that Xbox One will eventually supportexternal storage. PlayStation 4, on the other hand, will not, but you are able to replace its hard drive without voiding its warranty as long as it complies with certain standards.