the upgrade to 3.3 and later was for some posters here problematic, if they neglected to make sure that the library had no glitches. In that cases the upgrade of the library failed. So I'd strongly recommend to run all Aperture Library First Aid Tools, before you open the library in Aperture 3.4.3 to upgrade it to 3.4.3.
Also keep a backup of your aperture 3.2.x library and a copy of Aperture 3.2.x to be able to revert.
Just in case you run into this problem: Aperture 3.4: May quit unexpectedly on launch after updating
The above problem can occur, when you upgrade from certain Aperture versions, that have the wrong plugin-manager framework installed. Then you have to revert to an earlier Aperture version and upgrade from there.
The latest Aperture version requires MacOS X 10.7.5 or later. Is your profile signature current?
Good luck for the upgrade!
Thanks, Kirby. No it's not a typo: I've been of an "if it works don't fix it" mindset for longer than usual.
Thanks for all the info, Léonie. I've decided to do more housekeeping before I upgrade. I'm also going to break up my monster library. I'm long overdue to get the stuff that I'm just storing into its own library. I want to make sure that all of my important stuff is referenced- most of it is- and create a separate library for it. That way, I'll have a smaller, cleaner library to update, and I'll be able to get to my images from Lightroom or Bridge if Aperture breaks.
PS: when I relocate my masters with Aperture, I put four folders in the project folder: unrated, rated, highRated and topRated. That way I've at least got my ratings if I visit the images with another application.