This plugin is working fine for images that I add to posts, but when I set the same image for a featured image, it only loads the retina image on non-retina devices such as my iMac. It then blows up the image to its original retina size, and I have to go into my CSS and change the size in there. However when I change the size, it looks fine, but is still loading the full retina image (and therefore increasing load times on non-retina devices)
The image from this blog post if you drag it onto your desktop, you can see is a full-sized retina image. But if you click the blog post, the top image is the featured image (retina) but the one underneath which I inserted into the post is working fine and was created by the plugin.