I've been living with a new tankless water heater for about six months now. We have enough hot water to run the dishwasher or do a load of laundry while taking a shower at the same time. (It also provides hot water for our baseboard radiators.)
My only complaint about the unit is how long it can sometimes take to get hot water at a tap. I've gotten in the habit of starting the shower a minute or so before I intend to climb in to give it time to get warm.