The hardware is nice. The mini PCIe appears to be temperamental depending on which board you've used and there's little to no support from the vendor - they seem to have released everything, then disappeared.
All of them AFAIK. Even the Zero W can (finally) be had with relative ease, I just ordered one from SparkFun and Adafruit also has 'em in stock. Been wanting to make one into a security camera but they have been hard to get until just recently.
I think it depends on what is meant by "readily available". It's hard to do something like buy more than a couple Zero-W's at $10 apiece, unless things have changed very recently. In the past, I've seen people wanting to use a few dozen in a project having trouble finding that many for uninflated prices.
I can't see why they would though. I don't think the RPF has the resources to sell so many units at a loss. I suspect it's probably just barely breaking even on both. The Wifi chipset the Zero W uses costs exactly $5 in quantity according to Digikey; the board layout is slightly different but otherwise the bill of materials is the same so that's the main cost difference. They're probably making some profits off of the accessories like the case or the camera (especially the camera, which is pretty expensive and I expect fairly popular).
Very true. It's definitely hard to get more than a couple still. But they aren't perpetually sold out anymore, at least. That is definitely an improvement in the availability that has occurred in the past couple months, so maybe their supply is finally settling down.
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