I went for a master's degree (actually two) and don't regret a day or dollar spent. The upper division CS courses are wonderful for a mathematical mind. It brought together everything learned in undergraduate CS and Math courses into practical, real world, mathematical applications such as machine learning, natural language processing, data mining and others.

Today I'm a software engineer at a company that requires MS degrees for all their developers and it's a good environment - although I'm still looking for a place where I can leverage both my master's degrees.