Is the Waterfall software development methodology still viable?

Question

In my experience, it seems as though the Waterfall model has proven to be too inflexible and non-responsive to requirements changes to be considered a viable method in the modern world of software development. The growth and proven track record of more agile, iterative methods seems to indicate that there is no reason why anyone should be following a process of rigid blocks that assumes little to no changes from project inception to product delivery.

Is is the waterfall development methodology still viable for delivering software systems, with respect to time, cost, and quality?