The Simple WP Retina plugin does as advertised and swaps out images on retina devices to images 2x the size. It's perfect for getting rid of those fuzzy effing thumbnails.
One little problem though, it doesn't play well with all the different thumbnailed product images in WooCommerce. So I had to disable it.
I have pretty high hopes for this product because it certainly will save me a lot of time when the WooCommerce bug is fixed. So even though I deactivated it, I'm keeping it installed so I can see what updates are made and keep an eye on it.
If you're not running WooCommerce and want a retina ready WP site, do yourself a favour and install this plugin.