When the final crush dies off we have a "need" for 3 here as my first order. Even as a basic PVR and internet TV upgrade for old TVs out of the blocks RPi has a lot of potential. And as others have said, it's an awful lot of capability at very near the Arduino price point. I also have some old PIII hardware running Linux about the place currently for light duties and tinkering that can hopefully be retired and reduce our power consumption (and the heat in this room!).
Beaglebone and others are interesting, but the price point of RPi will I'm certain make a lot of people try it out and that can only be good for Arduino (at least in the short term) and hobby electronics overall. In the longer view, if the Raspberry Pi foundation can execute, and if the platform can live up to most of the initial hype, and once the RPi community grows and the ecosystem matures, Arduino could well become the remote sensing/hardware interface card of choice for RPi. It will certainly shake things up.
As for the choice of Broadcom, they used what they were familiar with and a company they had close ties to. That sounds sensible to me. Remember too, that we're not the ultimate target demographic.
I hope they can pull it off,
Geoff