Just read through Game Informer's article on the newly announced Elder Scrolls Online... so far its not inspiring much hope in me. There was a LOT of verbiage in the article that went "Well we know everyone really likes this about Elder Scrolls games, but thats too hard to do in an MMO". And I mean a LOT of that.
To quickly summarize the most disappointing aspects of the game so far:
You'll be playing from 3rd person, selecting skills from an "action bar" (jee that sounds soooo familiar

)
Player housing is (at least at launch) out.
Graphics will be stylized, with ZeniMax claiming that doing a more realistic Skyrim style of graphics with 200 plus players running around would be "impossible" (maybe they need to talk to SOE and the Planetside 2 team.... cuz they have thousands of players running around, and those graphics are damn impressive).
You will have specific classes instead of the "be what you play" model that made Skyrim so awesome.
Ok... now all that being said... some of the things they are aiming to do with the game DO sound fairly promising from an MMO stand point. I'm going to try and re-read the article and pretend I've never experienced the awesomeness of Skyrim, Oblivion, and Morrowind and will update with some good points for the MMO itself.
-UPDATE-
Ok, so here are some interesting tidbits that I think could make for a pretty refreshing MMO experience:
Three factions - All fighting for control of Tamriel (article says MOST of the continent will be open at launch, with some areas being saved for future expansions). Three races per faction.
"Hubless" quest design - Somewhat hard to understand from the article, but the gist: Instead of grabbing a bunch of quests in town, doing quests, turning in quests (ala WoW), just like in Skyrim et al you go around exploring and there will be quests at the dungeons, ruins, forts, etc you find. Example the article gives: You find an undead burrows and get a quest to clear it out. A spirit that you free by killing the necromancer in the depths of the burrows gives you the reward for the quest.
Stamina oriented combat system - Basically you can use stamina to block, sprint, interrupt, or break spells and attacks. The block may not stop 100% of the damage, but it will mitigate the negative effects (ie still take some damage from an ice bolt, but not be slowed by it). Great example from the article: in a PvP match, a line of melee class players charge (with their shields up to block) a line of archers and mages. Instead of taking a lot of damage and being slowed en route, they manage to get into the middle of their line. While they might be out of stamina by the time they get there (unable to block further), at that point its melee vs ranged in close quarters, and we all know how that will turn out
No "aggro" system... not quite sure on what they're using instead, but the article says ZeniMax wants it to feel more "natural". They talk about NPC's not just waiting around to get attacked... sounds like in Skyrim, if they see you, they're comin at ya, with melee types charging up to keep you busy while their ranged and magic wielding allies start filling the air with arrows and spells.
In relation to that last point: Smarter AI for NPCs - example given was you roll up on a "warrior" type, rogue, and a mage... Warrior rushes to engage you, mage drops a frost spell to slow you then gets out of range to throw spells, rogue circles in behind you. You have to prioritize and manage your stamina to make it out alive. Another example was a rogue dropping oil at your feet, with his mage buddy charging up a fire spell to light it up.
Cyrodiil (Imperial province from Oblivion) - One big PvP zone, factions fighting for control with the most accomplished player in the victorious faction being crowned EMPORER.... hope that comes with some nice perks
Of course, all of this is still under development and these things I've mentioned could (and probably will) swing one way or the other by the time the game is released.