It's been pretty bad all day for me, but it seems to have sorted itself out now, which is either a good thing (meaning it was temporary) or a bad thing (meaning it was a daytime issue which may return tomorrow).
I was experiencing latency from around 200ms to 1700ms+ as well as random disconnects, needless to say it made PvP a nightmare, even as a Warlock :P
Still killed a few gnomes though, so it wasn't all bad
EDIT: Just to clarify though, all my Internet usage was bad, not just World of Warcraft. Web pages, Usenet, Email, all of it was coming through at a snail's pace.