I did supply for a while and in some schools , with some classes it WAS an easier option, but only if the school was decently resourced, the classroom organised, the children reasonably pleasant and you weren't their tenth supply teacher in three weeks! It could be great if you were organised and prepared for anything. If it wasn't then it could be hell, no resources, no organisation, unfriendly colleagues, only one class ever reduced me to tears , but at home, not in front of them though.
I worked in settings I would never have normally worked in, like schools for children with extreme disabilities and nursery schools ,and though they weren't for me I loved the experience .
I usually left the classroom tidier than I found it, wrote copious records of what I had taught, marked work properly , still managed to leave at a decent time, always got asked back , and often got offered jobs!
The thing that makes teaching such a crap job is the constant unrealistic pressure. i went into supply after being driven to distraction by a particularly awful head, I wanted to leave teaching for ever, but what doing supply taught me was that I actually enjoyed teaching, being with the kids etc, so I eventually, by accident, found a proper teaching job that meant I could use my skills but craftily managed(for a long time, but they got me in the end) not to get caught up in too much of the madness. I stayed in teaching for nearly 20years after I decided to leave, so thanks supply teaching, you gave me back my career.