Huzzah! You'll be able to keep your gamerscore.
However exciting the Xbox One reveal was, the new console isn't all sunshine and unicorns. Recent reports reveal that the Xbox One won't be backwards compatible (understandable in light of the fact that the One's architecture will be completely different from the Xbox 360's) and that the One will require an additional installation fee for every new account for a game.
There is a light at the end of the tunnel, at least for gamers who obsess over achievements and Gamerscore. Microsoft has confirmed that Gamerscores will be ported over to the One, along with Gamertags and avatars.
"Your hard-earned Gamerscore will port over, so yes you'll take that with you," stated Xbox UK marketing director Harvey Eagle, "You'll also take your Gamertag, your identity with you. Whilst we're making a much bigger bet on natural identity with the camera, Avatars will also feature as well. All of the gaming identity that you have on Xbox 360 will be there on Xbox One as well."
So while you can't take your XBLA downloads with you over to the One, at least you'll be able to keep your ego intact with the points you've racked up with your time on the 360.