But I wouldn't say the capabilities of the device are limited in terms of hackability. You can easily flash your own bootloader, your own kernel and your own rootfs on to the device and do more or less whatever your heart desires with it. For ~$25 for one of these you get something pretty close to the imx233 developer board kits that Freescale sells for 400 bucks and up.
excuse-me does have a point, though, in that there is less likely to be vibrant chumby hacking community moving forward, though on the flip side of that there's tons of documentation already existing on how to set up a toolchain, how to get your own openembedded OS build up on the device, etc, whereas that sort of knowledge is going to take a while to build up for the Pi, especially if it remains difficult to actually buy one.
I totally agree with you on the Flash apps vision. This is such a shame that was the main function of the chumby in the first place. I was expecting to have both offline applications as well, and not flash based. Seems like that was not made to be.