The v1.3.1 hardware works perfectly. There are some tweaks to the programming process, obviously, and a few tweaks to the code, but programming the flash chip with "flashrom" both from a mac with a BusPirate and from a Raspberry Pi using its SPI interface is fairly straightforward. In fact, the Pi can successfully program the chip with an SPI clock of 20 MHz, which makes it much, much faster. If you're building your own version, you should check that flashrom supports the flash chip you want to use. I didn't do this beforehand and had to add support for it to flashrom for it to work right. The clock itself doesn't really care about what kind of chip it is, as long as a "0x03" read command works and it supports a maximum SPI clock of at least 16 MHz (it also obviously has to have at least enough storage for all of the audio samples).