I think there's a difference between a guy in a dress, and a transsexual. Imagine if they used an overweight woman instead of the facial haired guy in a dress! This seems much more lighthearted than if they'd used a large woman. I'm not saying it's okay to poke fun at transgendered people, I'm just saying that I don't see their particular portrayal as offensive. I mean, the guy looks like a construction worker. I don't mean to say that it's in particularly good taste (I haven't seen it yet - we don't have any Apple stores in Alaska yet), but certainly not offensive.
Now, if they used a real transvestite - someone who at least looks like they take their lifestyle a little more seriously, and didn't just slap on a dress for a few minutes - then it'd be way offensive.