The three major species of hemlock, mountain, western and eastern hemlock are low density softwoods. Hemlock firewood can put out a lot of heat but it burns up quickly.
As with a lot of the softer woods, hemlock dries quickly but also can hold onto moisture if laying on the ground or in a damp or unventilated area. It pops and sparks as it burns, which can be a hazard, but also nice for ambiance if you want a nice crackling fire. This makes it good for fireplaces and outdoor fires. It is good for starting fires and for kindling.
Post your experiences with burning hemlock below.