I think saying "support for basic media query syntax" and meaning that putting in syntax will not work, but will not cause errors is a bit confusing. Thank you for adding the additional info about the descriptors returning false to clarify that it's syntactic rather than functional support.
Since media queries were made a W3C recommendation in 2012, responsive design has become general. With things like Twitter Bootstrap that provide grid systems, it makes sense to support media queries for things like min-width/max-width, even if support for cyclic dependencies needs to be excluded still.
I was hoping to use Prince as a solution where I could do layout development of some reports in the browser and then render the final result to pdf with Prince. It looks great in the browser, but due to this lack of support, Prince isn't going to be useful for me.
I do not know whether the money left on the table by not supporting is enough to make it worth the development resources to add support, but Prince looks otherwise promising enough for me to check back in a few months to see if there's progress.
+1 for supporting this feature!