We have one. I guess I got it because it appealed as much as making a genuine rational judgement, but if I use the stove then that's the equivalent amount of gas not burned, so in part "a good thing". This far (5 years) I've only used found wood or leftovers from projects so there's some cost saving too, as well as said wood not ending up in landfill. It is supposedly compliant to the standards for city use, so I'd believed I was doing little harm and it was legit. Now that said, some of the more recent stuff I've read suggests even the compliant stoves (and not all are) are harmful in the particulates they emit, so it may not be entirely a good thing after all. I'm a bit more aware of such things having fairly recently acquired asthma and spent a couple of weeks breathing oxygen in hospital after a nasty bout of pneumonia.
Anyhow, on balance, assuming they are the pukka ones to standard with (somewhat) reduced particulates, I think leaving the gas in the ground and burning renewable wood, is surely better for global warming than adding more CO2 to the atmosphere. If we burn wood and replant, it'd be the same CO2 going round and round as it were. If the wood has a life as some manufactured item in between cutting down and going on the fire, that's even better.
I am conscious that if everybody had one maybe the local pollution might make this a bit leas tenable despite them being compliant to pollution standards
In the past I chose a diesel car because of the reduced CO2 emissions thinking I was doing "the right thing". There was no cost saving for me personally with the way my company car deal was structured, so if anything it was a slight sacrifice vs the more hooligan inclined petrol alternative. Anyhow the trend went against diesel subsequently for reasons of particulate pollution so it seem it was the wrong choice.