Really important, particularly in a class. That’s why I have one which springs closed automatically…..

That is definitely something I impress on my newbie quilting learners – there is far more likelihood of you cutting yourself with a swipe of a cutter being waved around in the air than of cutting yourself when the cutter is on the fabric – my instructions are always to close the cutter before (or just as you are) lifting it off the fabric, and only open it just as you put it down onto the fabric. If you can’t close your cutter easily, then invest in one that you can, as it is so important to be able to close it easily.