Normally, Torvalds enjoys seeing smaller release candidates as a kernel's development cycle ages, but this isn't the case for -rc3 with it being much bigger than last week's -rc2 version. Linus says there isn't anything particularly scary, but still he's not thrilled about the churn.
In order to see the Linux 3.10 kernel development doesn't drag on, he's going to see that 3.10-rc4 is smaller by being stricter about the changes he will accept and that he will be travelling for some days next week.
The Linux 3.10-rc3 announcement can be read on the Linux kernel mailing list.
In terms of the new features presented by Linux 3.10, there's a ton of new features and changes to excite developers, end-users, and other Linux stakeholders.