Some folks may be interested in my blog post about high-density displays and how using higher-density or vector images directly can greatly improve rendering and legibility of diagrams and charts:
http://leuksman.com/log/2011/12/04/high-density-displays-mobile-and-beyond/
If anybody's interested in fiddling around with JavaScript to swap in high-density PNG images and scalable SVG images (on either regular or MobileFrontend view -- though it's more relevant to MobileFrontend view), try this bookmarklet:
http://leuksman.com/misc/density-bookmarklet/ (source version: https://github.com/brion/density-bookmarklet)
It's fairly simplistic and won't work with everything. Attempts to replace PNG thumbnails with double-sized ones (may fail on some images), and rasterized SVG thumbnails with the original SVGs; but it does make some charts and graphs look much nicer on an iPhone 4 or iPod Touch with retina display!
Many Android phones have intermediate density displays (Android "hdpi" approx 240dpi, with the new Galaxy Nexus sporting an "xhdpi" 320dpi screen that's closer to the 326dpi Retina display); unfortunately the picture is complicated by Android 2.x devices not supporting SVG in the browser!
-- brion