Apple Thoughts: Cellular Connection Problems With The iPhone

"Some iPhone owners are still suffering from an issue preventing any kind of cellular connection, posters on Apple's support forums say."

I haven't had this particular problem, but I have been experiencing my iPhone 3GS switching between Edge and 3G frequently at work, which is well within the 3G coverage area. Never experienced it before the upgrade so it is possible my problem is also associated with the upgrade. Until I read this I assumed it was a problem with AT&T, and while it could still be their problem, it sounds like there is another possible reason.