I really suppose it depends on what is meant by open world PVP. At least in the STV area on a server like Fairbanks, which is apparently heavily Horde dominant, on a Sunday afternoon, there was mostly a lot of enjoyable PVP.
As a paladin questing with a warlock, we ran into mostly single or groups of two that we were able to overcome, if we were engaged. There were a couple of times we were outnumbered and out leveled, and thus were unable to achieve victory.
Overall though, I’d say the most challenging encounter was a rogue about 5 levels above us, who stuck around our bodies to make sure to kill us, if we rezz’ed. We had been fighting some mobs when another rogue about 3 levels above us, and a priest 2 levels above us decided to try to gain weekly honor by engaging us. We may have overcome this challenge, but here came this other rogue, and we fell.
Anyway, after about 3 or 4 times of coming back to our bodies, we were finally able to kill that one rogue who kept hanging around. After that, we quickly finished killing our quest mobs, and moved to the next area, not too far away. We did not see that rogue again.
I think overall, we got about 30 HKs, and died about 10 times in STV during the course of a level and a half, on a high population server, that is Horde dominant.
More to come, as we rise in levels during Phase 2, affectionately known as The Purge.