I tolerate them but would prefer if the formal nights went away. To me it is a vestige of a bygone era when the whole cruise formula was different than now. My observations on my last several cruises show me that most guests change back into casual clothes after dinner, so what is the point? To impress my waiter or the people at my table that I'll never see again? I prefer being comfortable and a jacket and tie is not comfortable. I ditched the tux 10 years ago. However I did wear a suit and went to a formal night on our recent cruise aboard Enchantment. We dined with the Captain so that was obviously a no-brainer about what I'd be wearing.
Also, it is difficult to accept how serious a cruise line is about formal nights when the waiters parade around the dining room in a conga line with the more talented ones balancing ketchup bottles on their heads. Sort of ruins the effect to me.