We had two in our home in Bailey. One was in a commercial kitchen downstairs and we rarely used it. The other, a Montague Grizzly, was in our kitchen. It was only a 4-burner but had a griddle and the oven. Pilot light propane use was negligible. We had two propane tanks. A 1000 gallon tank ran our furnace (I had that one placed when I started with the propane company I work for). There was also a 325 gal tank that ran only the stoves in both kitchens (it was in place before we bought the house). I usually topped off the 325 once per year in Sep...between 35 and 50 gallons.
I can't think of a downside. Loved the built-in griddle. Our insurance company never asked us about what type of stove we had...even though they knew we had a commercial kitchen.
The hood was loud but it was good at taking the extra heat out in the summer when using the oven/stovetop. I don't think the pilots added much heat to the house.
ETA: We didn't keep the pilots lit on the stove in the commercial kitchen. Only fired them up when we used it...a handful of times in 13 years.