Being quite geek I'm one of those early adopter guys. So wonder what? I've migrated my Aperture 2 library to just released Aperture 3. You may wonder why wouldn't I use Lightroom, but well, I just like Apreture's workflow + look and feel a bit more. That's it. Also faces and locations in Aperture 3 (apparently migrated from iPhoto) are just killer features comparing to Lightroom.

Migration was quite easy but it took quite a time to rebuild the Aperture's database to a new version. You can migrate from previous library, old vault or my way was to save (export) projects from v.2 to external drive and import them in v.3 one by one afterwards. This also helped me to clean up some older projects which were on standby for quite a long time.