Everything looks normal, and it's been a bit quieter than rc3 too, so hopefully we're well into the "it's calming down" phase. Although with the usual timing-related fluctuation (different maintainers stagger their pulls differently), it's hard to tell a trend yet.
Regardless, it all looks pretty small. I think the biggest thing in there is a skylake power management fix that came in as part of the gpu updates just before I was about to cut the rc4 release. Oh well. The other slightly larger change is some btrfs fixes.
But on the whole those things don't look that scary, and the rest is all really pretty tiny fixes spread out: various driver subsystems (sound, rdma, block), kvm, and some arch updates.
The usual shortlog below for the details -it's small and easy to scan to get a taste for the kind of things we've had.