AT&T is working on the issue.
Remember though, if you are used to a company like Sprint, there is a HUGE difference in the # of users, that can cause latency, etc.
You can put even just iPhone numbers up against all phones on sprint.
The main thing here is the jump to HSDPA 7.2. ATT is working on it and it should be completed around 2011. So little by little, the increased speed will be noticeable.
I think the issues you see with latency, speed, etc would be seen on any carrier, even verizon, if they added the # of webbased phone users on their network that actually use the webbased services like iphone users do. I am not one of those people that believe if iphone were on verizon, (exclusively) it would be all that much different.
No flaming necessary, its just my opinion.
In the long run, i think we are going to see some improved speeds, etc, and its good to see iPhone 3GS supporting HSDPA 7.2.