Do you like your on demand hot water heater?

We have a family of 6 with all of the showering, laundry, and dishwashing that goes along with this many people. We are going to replace our 40 gallon propane hot water heater in the spring. I would like to know from the people that are using on demand hot water heaters: Does the on demand keep up when you shower all six people one right after the other? Was it worth the extra expense?