Is biochar a good idea in terms of AGW mitigation AND soil fertility?

Do you think Biochar can be an effective aid in reducing/preventing AGW? Or do you see it as an over hyped 'bio-engineering' road to nowhere?

And for our friends the denialists who will undoubtedly do their thing and say it's useless because AGW is not real anyway, do you at least think it's a good way of adding fertility to soil, producing energy in the form of gas and oil, retaining water in soil, reducing air soot and therefore respiratory problems in developing country cooking stoves, AND while creating cost savings and even profits for farmers, companies, industry, countries, etc. ?

So in short, is it a good thing for AGW AND other reasons, and/or is it a good thing to do even if you don't believe in AGW. I'm asking this in good faith, as I feel that biochar might be something that AGW proponents AND deniers can agree on.