"If the UEs have poor power control and are taking more power than is necessary then it will sap the network’s ability to deliver high speed data.

“This is one of the reasons why AT&T has been sending text messages to users to persuade them to upgrade to the 2.0.2 software. In a mixed environment where users are running 2.0, 2.0.1, and 2.0.2, the power control problems of 2.0 and 2.0.1 will affect the 2.0.2 users...

"That explains why some users saw no immediate impact after installing iPhone 2.0.2, and why tests of individual iPhone 3G models showed no significant difference between the 2.0 and 2.0.2 software: the problem was only evident when a critical mass of phones all acted in concert to run a given cell tower out of power."

-- Daniel Eran Dilger