This is both good and bad news, depending on your usage habits. Mostly bad.
Check out the details of the new pricing here:
http://www.att.com/shop/wireless/plans/data-plans.jsp?WT.srch=1Sure, $15/mo is great if you use less than 200MB of data in a month, but notice if you go over that by even 1 Kb AT&T will charge you ANOTHER $15 and give you another 200 MB to play with,
even if there's only one day left in that month's billing cycle. I imagine a lot of people will inadvertently blow past their new limit, and be upset when they get their bill that month.
The key there will be watching your data usage religiously and know your billing cycle dates. Keep a sharp eye on it LAW, it goes quicker than you think!
The next tier sounds good: $25 instead of $30, but there's a few details to consider - $25 for 2 GB of data, then $10 for the next 1 GB of data if you go over. Notice that this
still gives AT&T more revenue than the current $30/mo for up to 5 GB "unlimited" plans. With the new plan 2-3GB = $35, 3-4GB = $45 and 4-5GB is a whopping $55!
Then they dropped the price for tethering from $30/mo to $20. Again, this sounds good, but it's a loss-leader: more tethering will very likely lead to cruising right past the new tier limits, and the extra charges for more data make up what AT&T is loosing by making the tethering cheaper.
They ain't stupid folks, this isn't about saving us money, it's about making them more off smartphone and iPhone users. This is why a $600 unlocked phone becomes $49.99 with a contract - they make it all back within two years, one way or the other.
The only good thing about this change is that those of us who currently have the $30 "unlimited" plan get to keep it, even if we upgrade or renew for another year or two. Kind of like rent control

Anyway, that's my take on it at least.