Sometime I use a lot - if you double-click on the part, it will show you the XYZ dimensions on the right-hand side. So if you ever want to verify how big a part is, that's another quick way to do it
Totally agreed!
Not so much for the overall size of the model (that you can verify by double-clicking the model) but actual measure function between faces, lines and vertices.
A lot of times I want to measure the thin wall thickness to make sure it's not too thin (this may also determine how many perimeters i should have), measure the distance from the build platform to the overhang/bridging, measure distance between 2 parts for sequencial printing so there are enough space to clear the printhead and the list goes on and on and on!