I'm on the AT&T grandfathered unlimited plan and so far have not been throttled despite going over 22GB every month. I've also lowered my talk minutes to 300/mo with rollover, which is still more than I need, so I save a bit there. I also got a discount for unlimited text. As a result, even with their just announced price increases for data, I'll be paying $80/mo plus equipment and tax/fees. I'd be content with this expect for the lack of tethering capability. I hate needing to buy more data for my iPad and being unable to use my MBP at all without wifi, so this is my only grip with AT&T.
I had never heard of AT&T's stream saver option until now, but I checked and it's off on my account. Seems like a nice feature since it's optional and not an up-charge to gain HD steaming.
Although these new plans from the competition sound appealing, another aspect I like about AT&T is how easily I've been able to use their Next Program to buy a new iPhone every year and receive it on launch day. I'm sure it's possible on the other carriers, but knowing how it's done with the carrier I have, makes me reluctant to charge.