Why does BBEdit look bad with retina display?
Edit: as of version 10.5, BBEdit has retina support.

I believe it's because BBEdit, like some other applications (Chrome, to name one) doesn't use the standard OS X text rendering library, thus it doesn't automatically get the Retina-calibre text, rather the text gets scaled up (like non-retina images), resulting in the blurry look.

Luckily the BBEdit team is working on it, they've released a beta version with retina support.