Character development looks amazing. Firstly, by ditching classes they've fixed one of my biggest peeves with Oblivion: that any discussion of character builds eventually ends with "put only controllable skills for majors". I've never liked that style of play. I play so I can kill stuff, have awesome adventures and feel like a Big Damn Hero. When reading about classes, I wanted an idea of what kind of builds would be balanced in a conventional sense, not what would allow me to grind for days and max my attributes. Additionally, perks allow me to feel like my choices are actually meaningful. Suddenly it matters what skills I choose to focus on early in the game, because while I may still be able to max all my skills eventually, I probably won't be able to make up enough perks to have a flawless godmode character. My character, then, is now a unique individual with strengths and weaknesses, giving me further incentive to start over and try a completely different play style.
Combat looks awesome. I felt like Oblivion was moving in the right direction, as combat felt far more tactical and exciting than Morrowind, but it did eventually become a little repetitive. Bethesda's stated emphasis on making combat in Skyrim a visceral experience has me salivating. I've seen it mentioned that blocks will be more timing-based now, and apparently that's unrealistic, but really? I don't care. Blocking added a level of tactics to Oblivion's combat that Morrowind lacked, and more emphasis on timing will only add to that. Also, magic. Spells are supposed to be more unique and epic, which is great because mage duels in previous titles were pretty lame. I might even consider playing a spellcaster for more than a few hours, this time around.
Atmosphere. Giant mountains and valleys are a lot more impressive than temperate forest, at least. And the presence of the civil war indicates that politics are going to be a much bigger deal than Oblivion, which I think will answer a lot of complaints about how Morrowind feeling better developed as a game world. Lastly, a bevy of fixes dealing with Oblivion's major flaws, such as correcting the ugly potato-head faces, the treadmill feel of the levelled world and the unresponsiveness of NPCs to the player's actions. ("You jumped on my kitchen table and sent my possessions flying across the room? Oh, hmm. I saw a mudcrab the other day.")
tl;dr unabashed fanboyism.
EDIT: They deleted the reply that went "Another one of these?", and that's sad. It made me lol.