So, did it work?
Yes, but, unfortunately, not very well. I was able to stream The Avengers (iTunes SD) to two devices fairly well, but once I added a third device watching the same movie the stream became unreliable. The device is supposed to be able to stream 3 movies at once, but perhaps they mean 3 different movies. Or, more likely, it can't really stream 3 SD resolution movies at once. I suspect it can stream 1 HD movie, 2 SD movies, or 3 movies ripped to iPhone screen resolution .
Since we have 3 kids, this isn't a great solution. We might still consider using it, but the SanDisk Connect 64GB Wireless Media Drive Streaming is supposed to be available in the next 1-2 weeks. It is less expensive, has much higher starting capacity , and claims to stream a movie to up to 5 clients (so probably 3). We've processed an Amazon return on the AirStash, but we may still keep it if we can't get the SanDisk in time for our trip.
Beyond the disappointing, but not surprising, performance issues I'll quickly list a few observations:
- It's a bit bigger than it looks in the Amazon photos, it can fill a good portion of an adult hand. It fit the chargers in our van, but for some USB chargers you'll need a USB extension cable.
- Although it has an internal battery, it's clearly designed to run off a car USB charger. The manual suggests leaving it in the charger.
- It's a pain to turn on/off. I'd kill for a simple switch instead of these quirky push buttons that require a manual to use. The indicator light is worthless when the device is charging, I found I had to unplug it to know it's power state.
- It takes about 15 seconds to boot up, so be patient waiting for WiFi to appear.
- The AirStash is controlled by the (WebDav client) iOS AirStash+ app configure settings. You can use this to rename it and play media. FairPlay DRMd media is passed to Safari , Safari in turn passes it to iOS QuickTime player (videos.app). As long as the DRM on the movie matches the iTunes account on the iOS device then the movie will play. There are no chapter controls, you can often move through the movie timeline but not always. For a single user movies play well.
- I was able to lock up iOS AirStash+ fairly easily and had to kill and restart it several times.
- On initial use I was told a firmware update was available. The installation directions were poorly worded, and, again, it's hard to see the power/firmware update status light when the device is charging. It worked after some fiddly.
- I don't think you can stream a movie when it's connected to a computer. I'm not positive, but it didn't seem to work in my testing. It's fine when connected to a power supply.
- You can put movies directly on the FAT32 formatted SD card or plug in the AirStash and it will mount. You can use Folders to organize your media.
- It comes with a plastic cap that doesn't fit on the end of the AirStash. So it will get lost pretty quickly.
- When I typed 'airstash.net' into my desktop Safari while connected to the WiFi I did not get anything back. It's supposed to show the file system, can't say why that didn't work. I didn't pursue further since I won't use the device that way.
- I didn't test how it behaves under prolonged load, but I'd be sure to keep this near a cooling vent in the car. Heat dissipation must be a challenge and prolonged overheating destroys devices like this.
- I was able to use a 64GB SONY SD Card with the AirStash, but I had to reformat it to FAT32 on my Mac. 
 The AirStash ships with an 8GB SD card, which is really only practical for testing. You can buy a 16GB version, but obviously that's a waste of money. Most will buy the 8GB AirStash then get a 64GB to 2TB SDXC card - but see .
 64GB internal, plus external slot available.
 It is perhaps not obvious why one would want this. It's a pain to put movies on/off iPhones when traveling, this way we could take our video library with us.
 I suspect the ideal use case would be someone who (illegally) rents Amazon DVDs and rips them to iPhone resolution, building a compact library that is streamable with a relatively low powered device.
 Safari is disabled on our kids phones as a minimally effective parental control measure.
 SD cards above 32GB come exFAT formatted, and the AirStash won't read Microsoft's patented exFAT. Which is how I learned that whereas Windows machines won't format FAT32 above 32GB, Mountain Lion will happily do at least 64GB and the (Linux powered?) AirStash will read it.
Update: My Amazon review (A minimally edited copy of this one). I'm going to test streaming from my MacBook Air.
Update 7/27/13: Ok, forget the SanDisk: "SanDisk’s drives don’t work with video content you buy from Apple’s iTunes Store at all". So they didn't figure out the Safari workaround AirStash uses. Guess we'll try to make the AirStash work after all.
Update 8/26/2013: We used the AirStash daily for two weeks and it worked quite well. Note we ONLY have SD movies and a lot of what the kids stream is animated and uses much less processing and bandwidth. Also, it was in practice rare for all 3 to stream video at the same time. So, despite failing my 3 stream test, it worked in practice. Kids had no trouble with the necessarily awkward viewing via Safari.
The biggest problem is that the AirStash, with its protruding USB and big body, is an accident waiting to happen. One child stepped on it and partly broke the plastic body. It continued to work, only insert with a flexible USB extension cable and making a protective container from a plastic "tupperware" dish.
The biggest annoyance is the on/off switch switch. I'd love a simple on/off slider. It was often hard to tell if the device was running.
Update 3/27/2014: You can use the AirStash to move files between iOS devices - including ePub files. It shows up as an option in the iOS share list in many apps; from AirStash.app use the copy function to move to AirStash device. Firmware updates are scary; if you plug it into a Mac you need to Eject before update will commence. Really, when doing firmware updates, plug it into a plain charger.