A teaspoon of The Hottest Fuckin' Sauce (600K Scoville) in my bowl of chilli, please.
Yeah, I'm a Ginger :)

I suggest you buy a local SIM, otherwise roaming charges will kill you. Think $1-2 per minute, or more, depending on your home carrier.
You will have to choose between AT&T or T-Mobile, they are the two (main) GSM providers. Both offer nationwide prepaid plans. Your N9 will work on both networks in 3G mode, your iphone will work on both networks in EDGE mode and on AT&T in 3G mode. In urban areas they're probably similar, but AT&T has significantly better coverage in rural areas. You can check their website for coverage maps. You can also check their website for pricing on prepaid plans (called gophone on at&t and pay as you go on tmobile).

I am more familiar with AT&T plans, since that's what I buy for my parents when they come to visit from Europe: the SIM costs $25 to buy, but it gives you $25 credit to your account so it is essentially free. Some clueless salesperson might want to convince you otherwise, but prepaid SIM card purchases are so rare they don't really know what's going on. You have a choice of plans, $0.10/minute, $0.20/SMS or if you're going to use your phone a lot, $2/day for unlimited voice/SMS access. You can also add a data package to this, which will cost you extra.

One thing you need to know about US cellular market is that you pay for incoming calls and texts at the same rate as for outgoing calls. This is compensated by the fact that rates don't differ if you're calling to a different network, either cellular or landline. Obviously, this does not matter if you decide to go for the $2/day unlimited plan.

T-Mobile's plans are different, I don't think they offer an unlimited option, and they are a bit more expensive, depending on your usage. Also, not sure you can get a data plan with them.

You are probably free to leave without paying an Early Termination Fee.

Yes.
Are you still paying different rates, depending on which network you're calling to?

Encoders often embed various metadata, such as timestamps, etc. Chances are same file, same software, same system, encoded twice, will result in different hashes.

Sprint is CDMA, there's no SIM card to be swapped there. Also Boost and Virgin phones are locked to their respective carriers, you can't buy from one and use the other for service.

The point of having an unlocked iphone even on AT&T is to be able to use a local SIM card when you travel. Another reason would be to use an AT&T prepaid account, which would be a lot less expensive than their regular voice plans.

I believe the problem lies at the interface between humans and software. It appears that in this case the software ran into a situation that it cold not handle properly, and the humans were not trained to recognize this limitation. Kinda reminds me of people that trust GPS navigators blindly and end up in a river or stranded in some desert.

IIRC, ENIAC was used to compute the trajectory of artillery shells. The following ones were heavily involved in the design of nuclear weapons.

I suspect your ISPs are not also large media conglomerates that stand to lose if customers enjoy unlimited high speed streaming