I've seen a ton of lag and spiking the past few days, both me and the person I play with, pretty much to the point where I'm giving up for the time being.
Tech support forum is, from top to bottom, nothing but lag complaints of the exact same symptoms and time frame but if you try to actually contact Blizzard for help they say that there are no known issues and blame your ISP. Nice.
Zero other issues on any other game or service, either.
Yeah, I'm pretty sure the lag in combination with a Vortex / Waller / Frozen Pulse pack killed my Hardcore Demon Hunter this afternoon =( RIP in pieces, Survivor.