I have the AT&T 10 GB share data plan. The "list" price is $100 plus $15 per device (devices off-contract price, either pay full price for phone or buy on Next installment plan). There are many FAN discounts of 20% or so, so check around, even ask the local store manager if he can find one to work for you.
This plan includes 10GB of shared data, unlimited T&T for all of the devices.
I have been very happy with this plan since it was first offered in Feb. or March of this year. A couple of weeks ago I took advantage of a short-term promotion and had the data allowance doubled to 20GB for the same plan price.
Had Verizon for 10+ years before switching to ATT. Very happy now, good signal in my home area (VA) and 4 trips this year to several states (NV, AZ, UT, WV, OH, MI).
Added note: Over the past 9 months or so AT&T has been very quick to lower prices and offer promotions, so pay close attention. In Feb. I received $400 service credit by adding 4 devices, 2 phones and 2 iPads. There have been several promotions since.