That's a pretty silly blanket statement.... I use my smart phone quite heavily throughout the week, but I tend to not do a lot of things such as streaming (Pandora, Netflix, etc).
I agree. Most months, I fit into the AT&T 200MB plan. And I have it sync'ing my email, calendar and I use it frequently throughout the day. But I leverage WiFi at home and in restaurants and coffee shops. If you have WiFi at home and at work (or school) then it's definitely possible to get away with a 200MB plan or less.
As far as the OP... I think it will be announced soon... like within a week or two. It will be available on all carriers in the US. And beyond that I pretty much agree with most of what Moose wrote.