There’s no advantage for me to use Monzo as my main card. I use a cash back credit card, and so would lose about £60 a year.
I use it for ATM withdrawals (very rare; I made my first withdrawal since the beginning of December last week) and for spending abroad as I get instant notifications in Sterling (it’s not exact, but close enough for me).
Yes, the contactless limit is £30 (unless you have Android Pay, presumably).