I don't run Aperture seriously, more out of curiosity, but it's frustrating that metadata is stuck inside its library until you export the masters, duplicating your files. That is especially annoying because I often go through new pictures on the laptop while watching TV, like United's annihilation of Roma last night, and the same master files are often catalogued by Lightroom and iView. Why shouldn't I be able to add keywords or captions to files in Aperture, then read that metadata elsewhere?

A partial solution is Lightbox XMP, an Aperture export plug in that lets you export sidecar files. Currently you have to specify a single export folder - it really needs an option that outputs the sidecars in the same folders as the originals. And it should merge with existing sidecars. Rather like Lightroom does….