I'm surprised
It looks like the same old deal we've come to know and hate from the operators, a bolt-on to an already convoluted plan.
Now, if I were AT&T&T&T, and I'm not, so what does it matter, I would take advantage of the fact that I'm going after an audience that expects things to "just work" and produce a plan that effectively does that. A straightforward "$99/mo" plan that does everything. Unlimited minutes, unlimited data (both internal and tethered), unlimited SMS, nothing else to pay except for some obvious exclusions (more expensive International destinations, international roaming.)
The way AT&T do their current plans, with roll-over minutes, free mobile to mobile, and free nights and weekends, makes this very close to what people get anyway. It's not like they, as an operator, make that much from overages.
I'm surprised that it would be another bolt-on data option. So, lemme see, you get 1,000 messages plus unlimited EDGE (but probably no tethering), plus 450 minutes, but 2,000 to use on nights and weekends, but some of them roll-over, see small print for details, etc. Wow, that really "just works" for us. Not.