The main locations you will be able to visit are http://www.uesp.net/wiki/Bloodmoon:Raven_Rock, Miraak Temple, http://www.uesp.net/wiki/Bloodmoon:Castle_Karstaag and a http://www.uesp.net/wiki/Morrowind:Telvanni_Tower (N.B.: Not the Telvanni Tower, but a Telvanni tower).
There will be some new armor types, http://www.uesp.net/wiki/Morrowind:Bonemold, http://www.uesp.net/wiki/Morrowind:Chitin, http://www.uesp.net/wiki/Morrowind:Nordic and http://www.uesp.net/wiki/Bloodmoon:Raw_Stalhrim each having heavy and light classifications.
Out of these new materials, you will be able to craft new types items out of two of them, namely Stalhrim and Nordic.
http://www.uesp.net/wiki/Morrowind:Spears will be added along with an array of new creatures/automotons, http://www.uesp.net/wiki/Lore:Riekling#Riekling, http://www.uesp.net/wiki/Lore:Scrib#Scrib, http://www.uesp.net/wiki/Lore:Netch#Netch, http://www.uesp.net/wiki/Lore:Boar#Boar, Benthic Lurker, Ballista Centurion, and something with an internal name of HMDaedra, quite possibly referring to http://www.uesp.net/wiki/Lore:Hermaeus_Mora since it lists his plane of oblivion, Apocrypha. You will also be able to ride dragons and be in combat while mounted on one.
http://i.imgur.com/gF1hJ.png is what the quest header for Dragonborn Quests will look like, and http://i.imgur.com/AJu91.png is what the compass markers look like for the new locations.
From the top, clockwise: Telvanni Tower, To Solstheim, Raven Rock, Castle Karstaag, Standing Stones, To Skyrim, Miraak Temple.
There will be at least two new tracked stats: Dragonborn Quests Completed, and Stalhrim Items Crafted
You will travel to Solstheim via a boat, much like you did in Bloodmoon, although this time, it looks like you may at least get a partial visual boat ride.
The Telvanni tower has float up and down animations, so no levitation it seems.
Dragon riding will take place in its own world space
Mounted combat looks like it's getting an improvement with the ability to cast spells while mounted, tihs isn't necessarily a Dragonborn only thing though!
It appears that Update 1.8 readies Skyrim for PS3 DLC.
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Misinformation:
Weapon degrading -- There's nothing to indicate this is added, that isn't to say it can't/won't be added however. There was just no "new" information in this update. The degradation stuff seen previously has all been renemants from previous CK games (Fallout)
Other stuff that I can't put my finger on or give intelligent guesses about because of lack of information
Miraak death animation, Chieftain animations, Chisel animations (perhaps new crafting station for the new armor.. doubt it though), Storn Death Reaction animation & Storn Suit Stages, H2H and H2H_AttackBash, H2H_Equip, H2H_Unequip - Not necessarily Hand to Hand, but it might be. Frea, Pray, StonePickUp, KillMoveDLC02RipHeartOut, TreeAmbush
There also seem to be a lot more animation files for running with weapons. No idea why.
warven Ballista -- Possibly a new trap? http://www.uesp.net/wiki/Skyrim:Dwemer_Ballista#Dwemer_Ballista
Previous Threads
http://www.gamesas.com/topic/1418474-18-betasolstheim-dlc-discussion-thread-21/