Oh, you don't like Ultrons look?
Seriously I don't get it. If you've read enough comics of Ultron one should realize that this is actually a very clever amalgam of Ultron's modern designs. Not only is it a unique design that can stand on its own for the film, but it's actually very reverent towards Ultron's character and personality in the comics. The conversion from the jack o' lantern ant-like visage to a face that resembles a skull is a very thoughtful acknowledgment of Ultron's very human personality and to say that it deviates from his character kind of defeats the whole point of Ultron's developmental process.
Also Transformers, really? Beyond having moving eyes and mouth, I don't ever recall seeing a single Transformer having the same smooth-plated, skull-like visage and curved antennae like Ultron here. In Transformers you could barely tell which parts were which with how their faces were designed. By and large, Ultron looks smooth and majestic in comparison. Heck it's not like Ultron got a complete makeover, the basic shapes and silhouette of his head is still very much Ultron.
And yes, the humanoid face might not be "classic" (ugh), but I'll have you know that Ultron's strongest form in the comics (so far) was very much human-looking. Considering the amount of fun I've had in finally seeing Ultron with a whole range of expressions in the comics, I have no doubt that this design will look utterly outstanding and creepy for the film version, judging simply by Spader's performance in the trailers.
Seriously for me, having been a fan of Ultron for so long it's like hearing people wanting the old skin-tight red/yellow classic Iron Man over his modern designs like the Extremis or Bleeding Edge armor. Yes it's just THAT weird.