I posted numerous times that I'll not use Dragonborn. I have lizardfolk for that, should anyone want to play a scaly PC. But generally, such freaks will be shunned by most humans and other civilised races in my campaign, we're not playing "sigil light" where everyone accepts reptiles in their neighborhood.
And tieflings - the PS tiefling beats the 4E tiefling since it can offer everything, from looks to backstory, that the 4E offers, yet offers far more possible looks and backgrounds. So, I see no reason at all to limit my campaign to the very narrow 4E tiefling.
As far as the 4E rules are concerned, so far they are not offering enough options to make switching an option - not enough classes, not enough customisations, no performance skill, not enough charm spells and other "fluffy" spells.
And our martial classes do just fine with the ToB.
So, what exactly does 4E offer to me at this point? Half the PC's can't be converted because their classes or prestige classes are not around yet. The fluff is not usable, and the new races are either unsuited or too limited. And for combat action, Bo9S offers lots of styles and stunts already, not that combat is that central to our campaign - we go more for plots, intrigue, and social situations.
Once 4E has (a lot) more options, especially out of combat, this may change.