The Exposure forum will give you plenty of information about how using the incident light metering and how, generally speaking, incident light metering is very precise and convenient.
Spot metering is the way to go when you want to place exactly the scene "tones" on your film curve and you have a scene, such as a scene with a wide brightness range, which makes exact exploiting of the film difficult. That happens especially with slide film. A spot meter will allow you to get an idea of where exactly the shadow will block and the highlights will burn in the final image.
For low brightness range subjects incident metering is just unbeatable, very fast, very accurate, no reasoning to make and no room for mistakes.