Spruce is easy to split, and catches fire easily. Spruce is a softwood, which means it seasons more quickly than hardwoods.
Spruce does not produce high amounts of heat, but does produce a number of sparks, which is a safety concern. Spruce contains large amounts of sap, which can get on your skin and clothes, and is difficult to clean up.
Overall, spruce is a poor choice for firewood, due to the low heat output.