Great idea to try it out before you completelly port over your number and closing your old AT&T account.
From what I heard in most refarmed areas you will get 3G speeds with your iphone but travel a few miles on either direction and you're back again to painfully slow 2G Edge data.
See if you can tolerate it and if coverage is there at the places you frequent the most.
With AT&T you dont have to worry about losing 3G cause its almost everywhere and now LTE is also available in many places.
So it wont be the same but if it works for you and you're willing to make some compromises then go for it.
From what I heard in most refarmed areas you will get 3G speeds with your iphone but travel a few miles on either direction and you're back again to painfully slow 2G Edge data.
See if you can tolerate it and if coverage is there at the places you frequent the most.
With AT&T you dont have to worry about losing 3G cause its almost everywhere and now LTE is also available in many places.
So it wont be the same but if it works for you and you're willing to make some compromises then go for it.