While there was a small leak a few days ago, the official word on the Xbox One update is out now and yes, you'll be able to add up to two external hard drives to your system to save apps and data.
For external storage, you need a USB 3.0 drive with 256GB of space and more. Plugging it in, you'll have the option to format and becomes the default storage path for content. You can manage the files, of course, moving games to your external drive from the internal drive and vice versa. What's nice is you can bring the HDD with all your games to a friends house, login on his Xbox One machine, and have access to all the content on that HDD without having to spend the time to download them from the server.
Real names is something that the PlayStation 4 has had and now it will be coming to the Xbox One. You'll have the option to opt in to have your real name displayed so you have a choice. You can also specify who you want on your friends list to have your real name displayed. This will work with friends and not with those who are just followers.
Smartglass gets an update as well with a ton of improvements with activity list, Guide display, and universal remote. A nice feature is you can re-order your pins on your Smartglass interface and it will update your Xbox One. If you use the TV feature, Smartglass will now display a Guide of your TV shows and you'll also be able to control your media center with the new universal remote feature.
There are some really good updates coming in June for the Xbox One as Microsoft continues to improve the experience both on the console and on tablets.