Not meant to be a shameless plug but I recently redid my business website to optimize for mobile as well. We didn't intentionally target retina but it turns out we're using a font for our logo and I'm very pleased with how crisp it looks on my Galaxy Nexus. I'm currently building a website for a client and the logo is a bitmap and there is distinct difference in quality. This is my own site, built with Bootstrap: http://www.electrichq.com.au