One of the topics we talked about indepth on last Saturday's WoW Insider Show was the racial ability revamp that Blizzard did in the latest beta patch -- I said that I wasn't even under the impression that racial tweaks were on the table, but apparently Blizzard still doesn't think they're done, and it looks like they're using those abilities to build in a lot of baseline things like threat reduction and resilience against movement-impairing effects.
After all the dust settled (there was one more revision in the works, and there may be more so far before the patch goes live), it looks like Shadowmeld is going to be getting one of the aforementioned threat reduction tweaks: Night Elves will be able to kick in Shadowmeld instantly and even while in combat every three minutes, and it will drop (though not wipe) threat, cancelled on moving. This adds, as Phaelia notes, a few new wrinkles to Night Elf gameplay -- not only will NE Priests have a new aggro "pause" (since the aggro doesn't actually disappear, all that will happen is that they'll have to wait for the tank to grab enough aggro to get focus back), but soloing Night Elves will have a new way to dodge a pull gone bad, and Druids who happen to be pulling in raids will be able to end a bad pull early, hopefully without wiping the entire group.
Pretty slick for just a racial ability. As always, this may change before the beta ends (originally, this was a Human ability called The Fall of Humanity, though Blizzard wisely decided it didn't work too well as that), but this extra functionality might give NEs an extra panic button when they need to switch threat around fast.