Ed: So many of you chimed in! We're thrilled you're enjoying the DLC. So after browsing through all the comments below, here are the 5 Most Important Things To Know about Dawnguard for those still playing or those waiting to get their hands on it.
1.Dawnguard or Vampires?
Will you join those who hunt down the vampires? Or will you become a "creature of the night" and defend them against the onslaught of zealots? Your decision matters. Bethesa did not cut corners on the story, and each arc should provide a fascinating tale all its own. Your decision all affects gameplay. With cool vampire bonuses, stealthy players my want to succumb to their darker nature in Dawnguard.
Finally, after so much demand, we can craft arrows. Skyrim has a pretty robust forging system that let people make some of the best armor in Tamriel, with one major oversight: arrows. The stealthy sniping-assassins had to constantly buy the finest arrows or pick up the scraps left be enemies. Now, players can make their own and remain fully stocked. Let the arrows fly!
3.A Richer World
User User:Allhail15 right points out that Dawnguard expands on Skyrim lore a great deal, particularly offering insight into Snow Elves. I also like Allhail15's suggestion that future DLC could include game specifically about the elves.
Without spoiling anything, just know there are many ways to become a vampire. Really, everyone should try being the living dead for a little while. Have no fear that it will ruin the rest of the game for you. The "illness" is completely curable, multiple times in fact. Oh, also, you can literally black out the sun to make traveling during the day easier. So feel free to become a vampire, and a "vampire lord", whenever you like - and trust us, it's worth it.
5. More Items
Some of the coolest items available in the game are released in the Dawnguard expansion. Crossbows, yes, are amazing. But you can also retrieve a Rune Hammer or an impressive magical shield. Just be sure you make yourself some bag space.