Responsive website design cheat sheet part 1: what widths should I design for?

Boom exactly, If you're thinking you need device specificity don't you really mean you need to be say; feature detecting for touch and increasing UI control size for that feature.

Detect zoom levels instead of getting the device and checking its resolution scaling.

We need to address the image scaling problems with a proper specification so unfortunately we're stuck with work arounds and guessing image size for that.

It was right in the initial talk about how to do RWD - you start with a design and then scale your browser and fix it at the widths it "breaks" at (stops looking aesthetically pleasing).

Unfortunately, that tends to require more effort than just creating a list of media queries based on common device sizes and only worrying about those.

Sounds like a cross browser issue, the fixed bar has a red background for me, Chrome, W8.