Replacing radiant boiler and water heater with combo unit

We got an estimate to replace our original boiler and water heater with one tankless combo unit, specifically a Quietside DPW120. Does anyone have any comments or experience with doing this or with this equipment? Would combining the boiler and water heater pose any long term problems?

Our boiler is on it's last legs, and will definitely need to be replaced. The water heater is in pretty good shape. But we were thinking of combining them to reduce energy consumption, save money, and space. Any thoughts? Any comments would be appreciated. Thanks!