The key is to have enough direct customer experience to trust your gut. When you start getting really conflicting feedback it's usually because the customers fall into different categories. Figuring out what those categories are is really hard to do without having a direct conversation with a customer and probing on it. For example with one company I worked with recently we had some customers crying for a particular feature and others that were completely indifferent. It turns out the folks that needed it were running in a particular environment, the others were not. In the end we decided that the first group wasn't big enough to warrant us doing the development and we decided against implementing the feature.