I find that conversion to black and white is a really useful tool for low-light pictures. Sometimes I end up with a color cast that can't be corrected, or with grain that looks bad in color, and both of these are actually pros for B&W images!
This picture is an older one, but I've never used it because the faces had a terrible red cast. I went back in and desaturated the faces for a partial B&W look which I kind of like!
These two were taken this month. They both looked ok in color, but I think they really shine in B&W.