Dataplan
Looking at this:
http://www.reghardware.com/2011/10/10/iphone_4s_tariffs_compared/
I get the feeling that most network providers will get rich. Only Three offers a flat rate, and seeing that SIRI does all the processing on the far end* I expect a lot of traffic if you want to use the cool new function. Oh, and probably also the iCloud photography/ video; cool, I can take hundreds of hires pics with my new iPhone and they turn up just like that on my iPad (dataplan?), iMac (dataplan?), MacBook (dataplan?) ... And no, the wifi isn't all that much of an alternative. It's a mobile phone, not a hang-around-at-Starbucks-while-trying-to-make-SIRI-look-for-a-cafe phone.
I expect a few guys will have to default on their mortgage at the end of the first month.
iCannot afford that.
*(it's not really a voice recognition software at all, you know? Apple built a giant call center in Bangladesh, Skypes your call through the web and each person that answers you after googling your question has their voice run through Autotune. )
Mine's the one with the iPatched elbows...