I dont have a OWB. I have had a lot of people tell me how great theirs is and a lot of people saying just the opposite. Personally, I am happy with my Iwb. Build a fire and instant heat. I made a heat exchanger for the stove to heat water, but it only works in the winter. I cant see burning wood year round just to heat water. I had let my stove go out a few weeks ago. Temps hitting 70F outside. Heck, I had to mow my grass twice in Feb. This week, back down into the 20F's. I looked at the cold snap as a chance to clean up leftover wood I had stored in my basement. Now that I am retired, it no big deal to visit the stove every now and then to throw in just enough wood to keep the fire from going out. And if I pack the stove full, it will easily burn all night, or all day, if I need it to. Wont burn two or three days unattended like a OWB, but I dont need it to. Weather being what it has been this year, I have been lighting fires only when needed. Some days building and maintaining a bast furnace fire, and other days just throwing on enough wood to keep the chill down, and other days just letting the fire burn out.