Since the NDA has been lifted, I want to ask some non-spoilerish questions mainly to Beta Testers, who should have finished the DLC by now...
-How many new armors are there?
-Are there alternate ways to contract lycanthropy?
-How Big is the Soul Cairn, do you only visit it once?
-Can you start the Dawnguard questline by joining the vampires and not the Dawnguard?
-Are there many -irrelevant with Dawnguard's plot- sidequests to do? How long is the DLC in overall?

I would really appreciate any answers given. Cheers to all 360 players and have fun!

Gonna get ninja'd since typing on my iPod is slow, but here goes.

Some. Faction armor, heavy Falmer armor, a unique set of Snow Elf armor...

Aela can give it to you one additional time. Random werewolf encounters do not give it.

Large and confusing, as you only have a local map. Maybe 10 times as large as Whiterun? Might be a bit of an exaggeration. You can return to it as many times as you like...and you will probably want to, for it holds many secrets.

No.

There is one big side quest involving the Dwemer. Dlc length is at least 20-40 hours, but it really depends on your pace.