So I finally did take the plunge and load this onto a Pogoplug E02. And while I have gotten it to load, let me say that getting it to work reliably is a major PITA. Amazingly enough, like Grayson, the image booted the first time without issue. But as I discovered further, biggest problem is that reboot's result in the PP firmware completely ignoring a USB device when rebooting which causes it to load the PP OS. But even that behavior is inconsistent, sometimes it will reboot and come back up with the PogoPBX image. So in order to hope to guarantee a "reboot" you have to shutdown and pull the power then repower. And hope that it finds the USB drive and boots from it. This is a problem for the E02 with other Linux flavors as there are several threads at various sites that give suggestions on how to deal with the problem but all of them I have tried have resulted in inconsistent results.
It's really a shame because the performance of the system when it's working is actually pretty quick. You can fully utilize the WEB GUI which means you don't have to make your changes on another Linux box or cloud instance. I think the processor speed of 1.2GHz really makes the difference over the PP 4. While the E02 is slightly behind the performance of my BBB running RASPBX, given the cost factor it's absolutely amazing.
I don't know if anyone at IPBX has some more time to spend massaging this image for the E02 but if you could get it to work reliably it would make a perfect SOHO appliance for a very low cost that literally is all-in-one (just plug in power, ethernet and a flash drive). And it's dual purpose, you wanna use it as a Pogoplug again well then just shut it down, pull the Flash drive and walla, it's back to normal. All for $15 shipped.
Update 10-13-14: Today I "dd"ed the image from the flash drive onto a real hard drive connected to the PP E02 via USB. Booting from the hard drive now, the observed behavior of inconsistent rebooting and shutting down has completely disappeared. What this tells me (and from what I have read has been alluded to) is that the PP firmware, once the uBoot has been altered to boot from USB, must be finicky about what it will boot from i.e. it must prefer real hard drives over ones that could appear transiently to be removable. So if PP thinks it's removable, it probably will reboot to the stock OS, if it looks like a permanent drive it will attempt to boot off of it.
Doing some research and looking at some of the flash drives on Amazon, evidently some of them can appear as permanent drives to the firmware or OS's of Linux devices. If you wanna boot the E02 reliably using a flash drive, look for one of these types which are often sold as Windows Readyboost compatible.
P.S. As you can see from the status screen shot, I added hylafax to the load but it's a work in progress - it tries to do faxes but something goes wrong and they are not received or transmitted even though the call is made. I may try to adapt the "install-fax" script from the RASPBX image and see if that makes it go but my gut feeling is that the PP doesn't have enough available RAM to properly render a fax image hence why it fails both incoming and outgoing.