The phrase "voting booth" is traditional. There's a reason for that. Casting a ballot is an act of conscience; it's supposed to be done in private so that those who'd pressure you to vote one way or another cannot ensure your compliance. Thus, mail-in voting is always less than ideal. It may be necessary under certain extraordinary circumstances, but it vastly increases the possibility of voter intimidation--think of a husband looking over his wife's shoulder as she fills out her ballot. So mail-in voting should be a last resort.
That said, Election Day should be a national holiday. The fact that it falls on a Tuesday inarguably advantages those voters who can manipulate their work schedules, which is undemocratic. But Election Day should be the only day on which you can cast an in-person ballot. Early voting announces turnout, whether light or heavy; that, in turn, affects the decision-making of later voters as to whether it's worth going to the trouble.
One final point: Not voting is also an act of conscience. It is as honorable as the decision to cast a ballot. "If you don't vote, you don't have the right to complain" is something people say when they haven't thought through the phenomenon.