@CodyGray Two reasons, one reasonable and the other very
spacebar heating–esque: 1) I am impatient and like shiny new improvements, and they're generally almost as stable as the non-nightlies (props to Mozilla). 2) I always have way too many tabs open, which consumes a lot of system resources. The "update and restart" button provides a convenient, fast solution to restarting the browser, killing all non-pinned tabs, and reloading with the tabs lazily loaded when I click them.