We have a fireplace. It's our primary source of heat. It's efficient, however - an EPA approved catalytic model. The smoke from the chimney is very light, and once it's burning dissipates very quickly. Plenty of stoves/fireplaces produce a blue pall of smoke that hangs over the entire area for days, and it's not one of those.
I'd be curious to know if studies included modern and correctly-installed stoves as well.