This may be totally unnecessary, but we actually had more patches come in this last week than we had for rc7, which just didn't make me feel the warm and fuzzies. And while none of the patches looked all that scary, some of them were to pretty core files, so it wasn't all just random rare drivers (although those kinds also existed).
So I agonized about it a bit, and then decided to just say "no hurry" and make an rc8. And after I had tagged the rc, I noticed a patch in my inbox that I had missed that was a regression from one of the very patches this last week, so that made me feel like rc8 was the right decision.
Anyway, maybe I should have just checked my email more carefully, and maybe I'm just being unnecessarily worried. I could have just untagged the rc release (it hadn't actually gone public when I noticed), applied the missing patch, and called it good. But instead I took it as confirmation that we should bake this thing one more week.
Confirmation bias? Maybe. Because while rc8 is bigger than rc7, it's not *hugely* so, and none of the changes look all that controversial. About 30% drivers (gpu, net, rdma, sound, scsi..), 20% networking, and the rest is arch updates, some mm fixes, some key handling fixes, filesystem, include files..
But on the whole I just felt happier with an extra rc than worrying about things.