Mine worked fine for the first 3.5 weeks, and then a few days ago just stopped charging. No connection sound when plugged in, no indication of charging.
I assumed it to be dead, so I replaced it with my iPod power adapter (same model) that's about a year old, and it's been working fine so far.
My iPhone also exhibits no charging problems when connected to my PowerBook.
I was planning to take the original adapter back to the Apple store for an exchange, but after reading the thread at Macrumors (
http://forums.macrumors.com/showthread.php?t=333933) decided to try it again today. Right now it's working fine, but I'll see how it's doing in the morning.