Intel Only
If I recall correctly, when Soundbooth appeared (along with the accompanying uproar about it being Intel-only) it was revealed that Adobe had either licensed or purchased outright audio technology written, from the ground up, for x86 processors. I imagine they realized this, w/regard to Soundbooth (note: the numbers are purely for an example, they aren't meant to be real-world):
* It would cost us 0 dollars to not develop a Mac version of Soundbooth, and we would make 0 dollars by not doing so (heh, this is obvious - I just thought this sentence was funny.)
* It would cost us 10 million dollars (and lots of time) to make a completely, from-the-ground-up Universal version of Sound Booth, porting the library (if this is even possible) and we'd make 5 million dollars on sales.
* It would cost us 250 thousand dollars (2 programmers for nearly a year, or something) of time to create an Intel-only version of the software, and we'd make 2 million dollars on sales.
Seems to make sense to me. I'd imagine Premiere is similar (although even greater scale, since it's more popular.) Also, consider that they wouldn't have keep both PPC and x86 versions in parity, as they release upgrades, etc...
Although I doubt I'll ever use Premiere on an Intel Mac, I'm excited because Premiere is an application that frequently comes up in lists of software that don't exist on the Mac (in spite of the superiority of Final Cut Express/Pro).