AT&T just announced new GoPhone data packages for prepaid customers that offer double the previous data transfer allotment (or better) at the same pricing tiers as before. The new monthly rates take effect April 22nd and will be available to those on either the $50 Unlimited Talk & Text or $25 Unlimited Text / 250 minutes nationwide voice plans. $5 will now get you 50MB of data (previously 10MB), which we still hesitate to recommend unless your mobile web needs are limited to the fundamentals: email and light browsing. Jumping up to $15 and $25 packages grants you 200MB (previously 100MB) and 1GB (previously 500MB), respectively. Some might argue those old price points were a bit unbalanced to begin with, but it's good to see that the carrier hasn't forgotten about its prepaid customer base.
Update: It seems customers will have to take some bad with the good. As pointed out in comments below (and in a thread at Howard Forums), AT&T is now requiring GoPhone users that want data to switch to one of the above plans, both of which include voice minutes. Previously it had been possible to take advantage of prepaid data packages while sticking to a pay as you go model for talk time — an option which will no longer be available going forward. The jump in data allowance might be more of a consolation for those that will now be dealing with a higher monthly payment.
Thanks, ssimpson205 and taosaur!