Back in June, Apple discontinued development of Aperture. A move that wasn't all that surprising considering how long it had been since it had received a major update.

While there isn't anything wrong with continuing to use Aperture, the lack of updates will mean that any outstanding bugs or new features will never be worked upon, so many are now switching to Adobe Lightroom.

Aperture Vs Lightroom has published a comprehensive migration guide, going far beyond Adobe's own PDF migration guide by covering everything from metadata to flags and labels.