There's not much to talk about, frankly, as this is more of a reminder that Age of Ultron is happening than an actual teaser. The follow-up to The Avengers will see the superhero team pitted against Ultron, a hyper-intelligent robot that can out-think, out-fight and out-whatever all of the Avengers. We can see a very brief reveal of Ultron's helmet / face, but not much else and definitely no footage, either. They've even recycled dialogue from The Avengers.
So far, Joss Whedon is confirmed to return as director and he's been somewhat apologetic about The Avengers' all-over-the-place script. We also know that James Spader will be the voice of Ultron and that the original Avengers - namely Robert Downey, Jr., Mark Ruffalo, Chris Hemsworth, Scarlett Johannson, Samuel L. Jackson and Chris Evans - are all set to reprise their roles.
It's kinda weird that this is going up first, ahead of teasers for Captain America: The Winter Soldier or even Ant-Man. We're guessing they're trying to push it on the success of the Avengers instead of the individual stories. Anyway, check it out and let us know what you think!