I've been working on firmware examples for the new featherwing. Right now all of the examples use circuitpython. I haven't put in an online repository yet. I will do this in over the next few days. I've been pretty pleased with how well circuitpython has worked for this - very easy and quick to program.
Right now all of the firmware examples just stream the data back to the host PC over USB. I am also pretty excited about trying to make some standalone devices which use feathers such as the pygamer https://www.adafruit.com/product/4242 which have a display, battery connection/charging, SD card, etc. The rodeostat featherwing can be plugged directly into the connector on back. It seems super nice for making a battery powered portable device. The pybadge is also interesting https://www.adafruit.com/product/4200. I think both are still available from Digikey.
We should have the featherwing PCBs available in about two or three weeks. There is some uncertainty on when we will receive the PCBs ... not surprisingly.