This plugin works great for videos that can be embeded using url oembed, or as objects; but it does not expand iframe embeds to fill the container.
<iframe frameborder="0" width="480" height="270" src="http://www.dailymotion.com/embed/video/xyrosa"></iframe>
For iframe embeds I am using the Advanced Responsive Video Embedder, which places a short code into the post.
But I would rather simply embed a video and have it work, and for most of my needs, FitVids for WordPress is the best. Thank you Kevin Dees!