Ebon Shar said:
Now why would that be a deal breaker? I've known people who could not stand halflings. They simply choose not to play them. Why does the arbitrary inclusion of a race that you don't like disquality an entire edition of the rules? If you find that 4E is right up your alley, the best thing to happen to D&D since the flumph, would you still refuse to play, or would you simply disallow tieflings in your campaign?
I think of Tieflings as a PC race in the PHB as a deal-breaker, but not by itself. It's a sign of a pervasive attitude that seems to fill 4e, the disregard of established setting presumptions and meta-setting information.
As was pointed out, the 4e design staff are not longtime D&D design veterans. We don't have the likes of Skip Williams who had been with D&D since the early days at work here, we have people who are excellent designers, but ones with not as much investment in the traditions of the game and as dedicated to making a game that is as much a continuation of what came before as a good game in its own right.
When 3e came out, one reason I knew a lot of longtime veterans switched over was that it had a lot of respect for what came before with D&D, it brought back things that hadn't been in 2e but in 1e (Assassins, Monks, Barbarians, Half-Orcs), it acknowledged Greyhawk as the standard D&D world (at least in theory). 4e dumps Greyhawk, it dumps Monks, it dumps a lot of the "legacy code support" that made 3e popular to some veterans.
Previously, Tiefling PC's were treated as something possible, but only on the fringe. They weren't PC's at all in 1e, not in any official source I know of. In 2e they were a planescape-specific race. In 3e they were included in the FRCS but were still implied to be rare and generally only found in a few places and Tiefling NPC's were very rare. In 4e they are going right into the PHB. . .replacing Gnomes that had been there since 1e. Out goes something people expect in the core rules of D&D (and not the newspeak definition of Core), in something comes that is not associated with the main body of the rules. The races in the PHB are generally assumed, or at least are by the gamers I know IRL, to be the most common ones in the gaming world. So, D&D 4e now presumes gnomes are so rare as to be a "monster" race, but Tieflings and glorified lizardmen are as common as gnomes once were.
D&D before had been built to have a presumed flavor, and that was a pseudo-medieval theme, a little Tolkienesque, borrowing in places from a few other fantasy sources, and in some part a library of it's own unique setting presumptions. From what we've seen so far, 4e is throwing out the pseudo-medieval Tolkienism and the unique setting presumptions for a different flavor and set of setting presumptions altogether.
So, tiefling PC's in the PHB might not be the reason to skip 4e on it's own, but it's a symptom of the design mentality which is chasing some of us away.