I know I have posted a month back about this calculator, but this video unboxing and test, is really entertaining to watch (as testified by the over 430k views so far). It just makes me want to have one, although I really don't have a need for it (I have an HP41CV if I really need one).
The DM42 is a clone and improvement of the famous HP42S, with open source firmware based on the Free42 platform. SwissMicros has done an excellent job though on the build and presentation. It is also an excellent example of how repairability should be done.