4th edition tieflings are an entirely different entity from the previous tieflings in appearance, backstory and, for the most part, concept. 4th edition tieflings look remarkably like draenei. Looks matter most, because your first impression is from the art.
Y'know, it's probably my Planescape bias, but I love the idea of tieflings as orphans, social rejects, and general outcasts, looked askanse at because of their "different" nature, necessarily assumed evil even though they aren't necessarily evil.
It's a really great RP vehicle to trot out concepts like social equality, to play with the medieval idea of "your blood is who you are," to twist this idea of self-determination when you are literally part of the evil of the planes, and even to work with concepts like race and class divides in a fantasy context in a way that's maybe a little easier to buy than goblins or orcs or the like.
These new tieflings with their ancient empire and their evil pact and their "no one really holds it against us but look how
almost evil we are!" don't have the same juicy RP potential. They might have some different potential, perhaps more suited to Swords and Sorcery, but as a fan of urban fantasy and fantasy-as-allegory, it's less suited to the kind of games I like to run.
But the new tieflings aren't draenei knock-offs in anything but artistic style (and even there, they are "different enough" because of their accessories and style of dress and the like). Art matters, and they have similarities, but they remain pretty distinct.