I also agree with Tab and Jeremy on this one - that makes a lot more sense to me and removes any ambiguity without being overly verbose.
> I asked: >> Related question: do we still want to keep this unit-less i.e. ditch the >> "px" from the examples above? Or, if we're going to use this CSS-like syntax >> anyway, allow other units of measurement (e.g. ems). > > And Tab replied: >> No, if we're aping the CSS syntax more closely, we should just use CSS units. > > I agree. Seems like the sensible approach. It also allows authors who are > using ems for their media queries in CSS to also use ems for their srcset > declarations. > > Jeremy