I contemplated returning it.
Then deep in the bowels of the Kindle discussion groups I came upon this thread. So I started to play around with my wireless access point. I use an Apple Airport Extreme (APX), with an Airport Express as an extender. There are lots of devices connected to this network – at least a dozen (PCs, Macs, tablets, phones…) – and they all work flawlessly. I’d configured the APX WiFi as “Radio: Automatic”. I switched it to “Radio: 802.11a/n – 802.11b/g”. Instantly the Kindle Fire started working properly.
I still need to run a few tests to see if this change has any negative impact on the rest of my network, but right now I’m happy to have a usable Kindle Fire