1. If you already have a licensed copy of Aperture in your Applications folder, you need to move or rename it before installing the Aperture 3 trial.
Fine. I renamed it ‘Aperture 2’.
2. To open an Aperture library with an older version of Aperture (1.x or 2) after you use the Aperture 3 trial, drag the library onto the application icon of the older version.
OK, now I'm slightly confused. After using the Aperture 3 trial, which I'm about to learn won't allow you to upgrade an existing library anyway, I don't just go and open the newly renamed ‘Aperture 2’ application, I have to drag and drop my existing library? Aperture 2 will mysteriously forget where my library is? Although I back it up (using Aperture's in-app ‘vault’ system), I get pretty nervous about my Aperture library, particularly as it's a ‘managed’ library—there's not a lot of transparency about where my photographs are.
3. The trial version of Aperture 3 cannot upgrade a library created by an older version of Aperture. This is only supported in licensed versions of Aperture 3 since it permanently upgrades the library.
That's fine, and not unexpected, but by this point I was still trying to decode what was going to happen to my existing library in the unlikely event that I didn't buy an upgrade license and wanted to revert to Aperture 2.
I considered not installing the trial version at all, but I was very keen to see it. The Apple Store seemed to suggest that I could just purchase an activation key online, and that I wouldn't have to wait for a box to be shipped, but last time I tried that (with iWork '08, if I recall correctly), the claim was just flat out wrong—the Australian store simply wouldn't sell me an activation key online. Anyway, I downloaded and installed the trial. At the opening dialog, I was offered the chance to purchase the activation key, so I tried it. Safari fired up the Australian Apple Store, and I could, indeed, purchase a key on the spot. So I did. Apart from the slightly confusing email regarding the trial, everything was particularly smooth. I've just fired up Aperture 3 to check out the new features. This could take a while.