Brian
You’ve been here awhile so you know well what you’re getting into, even going from 2.3 to 2.4, there will be things that need changed or adjusted. Obviously, starting with a backup and test on a new SD card makes good sense. 2.5 is a much improved version over 2.4 and M3 is pretty stable.
First question, do you use Hue emulation? If you do, you may want to stay with 2.3 because Hue emulation is broken in 2.5.
What Marcus said is important since you mentioned z-wave. All things will need recreated.
Here is the M3 testing thread, there are a few outstanding other issues
