QGIS » QGIS Application

I had explained in a lot of different bug request that QGIS Set Layer CRS is a lottery, and works in mystical ways.
Sometimes it works if you load the saved layer into another QGIS instance.
Sometimes it works if you activate OTF
Sometimes it works if you deactivate OTF
Sometimes it works if you change the LAYER CRS
Sometimes it doesn't

Sometimes it works if you change the project SET CSR
Sometimes it does not work at all.

I am using QGIS for over 3 years but i had never understood how do you really change the CSR
I am holding trainings and teaching other people how to use QGIS and still this is a mystery to me.
Let`s think how to make QGIS more friendly to use

Maybe i don`t even need to learn how to change the CRS, but there can be a simple setting in Distance Matrix Plugin to choose for the users that are not so advanced and don`t understand how to change the CSR to have a option - output in meters , output in miles, etc

The default is in map units, a function that 80 % of simple users will not need, especially when i will know that the distance is 0.0021 arc maps just want to know the distance in meters between my points, and it should not require 10 google search and 1 bug request to accomplished that.