Looking at the video, the thing that impressed me is how much more satisfying the combat looked than Skyrim. It looks functionally similar, but the spells in particular seemed to have a much weightier feel to them, like they were actually a force of power instead of just lights on the screen. That was my biggest problem with Skyrim's combat - it didn't feel tactile or kinetic enough, and hopefully ESO will improve upon that.
As for the mods, while I highly doubt that you will be able to add many game-altering mods, given that this is an MMO, it will certainly be nice if those with high-end PCs can install graphical mods like we did with Skyrim and the others. It would be really cool to be able to play on modded servers though. I'd love to see an MMO version of Skrim's Requiem mod, that would be nuts.
The other thing I noticed is that the spells looked more interesting. The cage of bone is a cool spell, and that burning chain that pulled the enemy toward you in the video was awesome. The spells in Skyrim were sort of bland. All of the destruction spells just hurt people, all of the alteration spells buffed or protected you, all the conjuration spells summoned familiars to fight for you, and the illusion spells were never necessary. If they can spice them up, it will go a long way toward making being a mage more fun.
All in all, I'm a lot more optimistic about this game after seeing this article, I wasn't too sure about it before, but it looks good.