I'm using a Retina MacBook Pro and it's also blurry for me. You should multiply the canvas "width" and "height" attributes by devicePixelRatio, but keep its size constant using CSS.

In my case, a retina iMac with Firefox. See http://www.html5rocks.com/en/tutorials/canvas/hidpi/

I'm using Firefox on a Retina MacBook Pro, and I get low-DPI rendering; Chrome also does low-DPI rendering, but with better anti-aliasing. The text rendering looks even worse on Safari; it doesn't even appear to do proper hinting, so the widths of characters come out all uneven, though oddly it seems to antialias the largest text, your name, but not any of the rest of the text.

From worst to best, Safari appears to have inconsistent antialiasing and no hinting, Firefox has no antialiasing, while Chrome looks the best with antialiasing. They all look fairly blurry and out of place.

Chrome on a rMBP.

I'm using Chrome 42 on a non-retina MBA and it's blurry for me too.