Linux kernel 3.8 RC7 is comprise of mostly drivers updates for networking, Radeon, USB, sound and regulator, but it also includes patches for other stuff, such as for the Btrfs filesystem.
"Another rc from Australia, just before heading back home. It still hasn't been as quiet as I'd have preferred (and with the absolutely horrendous internet access the last week, any pull at all was pretty painful - git is good about network bandwidth use, but it still wants a network that stays up and doesn't lose packets left and right). Anyway, here it is." Linus Torvalds said in the official announcement.