There was a nice comparison of all the major US providers in the US at Engadget a few months ago. Verizon was by far the most expensive. Extra chargers for tethering are the norm, sadly.
I didn't mean to say that AT&T was the only one charging for tethering, far from it. Just that it's ridiculous that if I were to decide to use tethering on my iPhone, I have to pay an additional fee on top of my mandatory $30/month "unlimited" data plan. So I'm already paying for unlimited data, but it's only unlimited if that data comes from the iPhone natively? That's ****, and we all know it. Unlimited means unlimited. Could one argue (i.e. class action lawsuit) that AT&T is guilty of false advertising? I'm paying for unlimited data, but not actually getting it, should I decide to use tethering.
I know there's the argument that AT&T would incur an influx of stress on their network if they didn't charge for tethering, but to me, it's shady at best. How about finally getting around to beefing up your infrastructure instead of blaming users for crippling the network?
Heavy is good, heavy is reliable. If it doesn't work, you can always hit them with it.