Well, they actually *can* reset your data to full speed again. They did it for me once, and I had to shut my phone down and restart it after the rep did something on their end. However, this was when I was throttled and the speed didn't automatically reset after the new billing cycle started--so they were *willing* to do it.
At any rate, its not the reps fault--they don't have the authority to unthrottle you so I try to remember that when dealing with them. They are human beings just trying to get through the day.
AT&T service is mostly good, and better than T-Mobile right now overall by a significant margin. That's why I'm sticking with them even though T-Mobile has true unlimited data still. However, in about 5 years I think AT&T and T-mobile will have comparable coverage and speeds so we'll see.