During a keynote speech tonight at the 6th annual Vidcon event, YouTube CEO Susan Wojcicki announced a new version of its mobile app. Available on Android and mobile web browsers now (iOS coming soon), it makes it easier for creators to publish and edit directly in the app, and easier for viewers to subscribe to a channel with just one button touch (and with ten million of those touches, channel owners can earn the new Diamond play button reward). The redesign even puts your subscriptions and profile right at the top for easy access. This is also the version that adds the ability to watch those vertical videos in full screen, so expect that to come your way soon if you don't have it already.
Update: An update to the iOS app is out that brings fullscreen vertical video support to your iPhone too.