Firstly, what is it? Bio Char is a name for a 'oxygen free cooked' organic charcoal, primarily found in Terra preta, an amazing soil found in the Amazon Basin.
Turns out, this charcoal cooked under Pyrolysis has a unique structure, beneficial to roots and mycorrhizal fungi. It similar to Zeolite and other products.
Just seeing if anyone is interested in trying it out in some pots. I'm about to, but don't have the bonsai/repotting experience to offer any objective judgements. I live close to a Biochar producer and am about to pick some up, sans freight.Biochar improves the soil texture and ecology, increasing its ability to retain fertilizers and release them slowly. It naturally contains many of the micronutrients needed by plants, such as selenium. It is also safer than other "natural" fertilizers such as manure or sewage since it has been disinfected at high temperature, and since it releases its nutrients at a slow rate, it greatly reduces the risk of water table contamination.
From what I understand, it holds a lot of water and works far superior if you soak it for 2 weeks in an organic fertiliser/compost so the charcoal holds nutrients in those micropores. Plus, it lasted 2000 years in the basin, so could easily be added to your gardens after repotting.
Bio char sounds good thoiugh, man made, thanks for the info. We have been adding a little charcoal to our kanuma mix for azaleas lately ( another tip that Arthur brought back from Japan) it keeps the mix 'sweet' - whatever that means ( not sour, too alkaline???). The bio char may do this job too, aswell as holding and slowly releasing nutrients 
