Today at SHARE I had the remarkable experience to listen to a session Connor Krukosky. He's a 18 year old student that bought a z890 on eBay. Here is his story. The first operating system he got running was Linux. Some of the stumbling blocks (e.g. writing a IOCDS) he mentions reminded me from the time 17 years back, when I learned the same things the same way. SHARE has recorded the session. The video is now on YouTube:
(updated 3/29/2016)