So...yeah. I hope that this isnt going to be a trend. I didnt care for the 30+ elf subraces in 3rd Edition, and I somehow dont think that 4E will make it any better.
Dusk elves are elves that have the Dusk Elf Stealth feat. Apparently this makes you pale, emo, and wear clothing that you pillaged from a Ye Olde Hot Topic. You also grant allies (and only allies) a bonus on Stealth, but its mostly a gateway feat for the rest of the Dusk Elf feats and paragon path that makeup the article.
I dont much care for this article as it stands because I think its stupid that a bunch of elves that run away from a big battle undergo radical physical changes and gain chronic depression. Its like vulcans gone sad, except that when alone or with a "trusted few" they give in and I dunno, smile.
It doesnt make much sense from a narrative stance, and honestly I would prefer to think of it as a more clan- or family-oriented feat tree. Some elves are just really good at hiding, I guess. Perhaps its a result of a connection or exposure to the Shadowfell? Shit, they worship Sehanine: just say its a boon that she provided them with. Sounds better than, "they ran away and got super-emo powers."
Anyway, there are six feats that do stuff like give proficiency and damage bonus with all light blades, make you invisible when you have concealment and use total defense, and add your Wis mod as extra hit points when you burn a healing surge while hidden. Interesting, and works well with an assassin or rogue concept.