Specifically the 5 volt, 16Mhz version. The biggest hiccup in getting the first demo program to work was 1) getting the right cable, and 2) working around a cable issue.
Once we had a cable with data, it turned out there was some timing issue with the latest chips and some marginal cables which we happened to buy. Had to find and old hub and route the USB upload connection through it to use our cable. You will see a device added to the USB bus, and it should succeed when uploading blink. Then the device will blink and you can try your own experiments.
Please report issues you have. You can start in the discuss function on this page.