YourTube is primarily designed as a solution for the age-old problem, and it is quite well at doing that. YourTube supports downloading playlists, major automation for quicker work and downloading video in the highest available qualities.
What is new in this release:
Version 1.3: You can download audio and video now. Better playlist handling. Better audio tagging. More customization in settings. Better UI design.
.NET Framework 4.6