Well isn't it kinda assumed if you can trade used games its assumed you can play them?
You might think so, but you could be wrong.
XBone is basically a digital platform. The discs are just a method to get the game -- don't want to download 40gb on the day of release? Drive to Best Buy and get a physical disc. Get home, pop it in, associate it to your account. Now the disc is useless. Nobody else can use it to install, your game is on the cloud and associated with your account. So if the system DRM policies are set to make the disc useless after the initial install so you can't just give it to all your friends for free. So unless the game can magically be reverted to "new" status in the Xbox database of games and licenses, which a retailer like GameStop would need to verify before giving you any credit, there is no way to play used games.
Here, think of it this way. You can't use GF with the XBone the way the new DRM policies are stated -- the first person to rent it would permanently own the game. Then what? You send the disc back to gamefly and nobody else can use it. So unless, as I stated above, there's a way to revert the game's status to "new" when you trade it into a "participating retailer", used games aren't likely.
If the above is true, I'd guess the trade in/selling would work like gamersgate -- where you can somehow trade in your license and disassociate it from your account to Microsoft (or maybe GS online or something if properly integrated) which will get you credit you can then use to purchase a different license. The question, again, is can the license be restored to a particular disc after it has been associated with an account, and if so, how do these participating retailers verify it so they can accept the trade in. It all depends on that for the XBone.
this is a hideous

ing website
Even with the dark theme it's pretty hard to read now. Visually it looks like there's too much going on.
I actually think I like it better than the old version -- it's cleaner to me... I find it easier to read now that my retinas aren't burning out of my eyeballs. I just wish I could fix my posts per page now.
At last testing, ignored posters are very understated and I had to try very hard to find any evidence of a post existing... it's very well done, IMO. I'm digging it. :shrug: