Thank you for the link to respond.js, it does much more than my script fragment(supports inline @media in stylesheets).
Looking at the source for respond, maybe i am misunderstanding but the script looks like it will re-download each of the stylesheets in that page to bypass the IE parser(which throws away any @media statements).
I am thinking this re-downloading of each stylesheet on slow links will cause flash as page is laid out again with the @media style info included.
The script have above just switches a stylesheet to enabled when page is loaded, implicitly assuming IE can parse it. Obviously in such a scenario inline @media won’t work but it should also be faster hopefully avoiding flashing.