A: It forces you to get used to using cold water!
Sure, once you are in the shower, there is hot water forever. But, if you have the habit of tapping the tank or flicking the faucet for that quick spurt of hot water to brush your teeth, wash your hands, rinse off a dish or cup, FORGET IT! Hot water is just no longer there for you the way it used to be.
We will adjust to it. It’s not that bad; probably a good thing in the long run.
Another major advantage to tank-less is that the old large tank holding gallons of hot water, and aging ever nearer to its moment of structural failure, is no longer in our basement waiting to burst forth and soak all the old books and magazines we’ve stored down there next to it. (Now there’s room to store more books!)