This seems like a poorly reasoned article to me. I don't think anybody argues the point that AT&T has the fastest 3G network. You can have the fastest network. It can have slightly more signal bars. It can also be the one that drops calls the most. These things are not mutually exclusive.
There is also more than signal bars. AT&T works fine at and near my home, but it works awfully at one city I travel to. I get full 3g signal bars there, but websites time out, except at night time, and many incoming calls don't get through to me (going straight to voicemail). So yes, technically I get great 3g signal there, but their network there simply can't handle it.
I recall reading rumors when AT&T's network quality first became an issue that they were upgrading the radios at base stations in major cities, but not the backhaul capacity. Not sure if it's true, but it would explain why you get full bars without any bandwidth.