The new Aperture 3 library management is fantastic, I've always used multiple libraries and when I just wanted to take a specific project with me someone I'd previous had to export the project then import it into a new library then export it again and re-import it. It worked just fine apart from the fact that it used up lots of extra space and was cumbersome.

With Aperture 3 all of that is a thing of the past. I used the export library option extensively yesterday as my wireless network was playing up, the feature is a dream to use.

1) I'd created a new client folder and project in my current library, culled and tweaked the files ready for a viewing.
2) I then exported the project as a library:

3) This created a library called Pippa, I exported it directly onto an external HD that I could then hook up to my MBP
4) The client viewed the files, was very happy, spent some money :D (making me very happy!) and off they went
5) I opened up the master library, clicked on import and selected the library on the external HD:

Aperture 3 automatically recognises that this matches one of the projects and asks if I want to merge the two. I click yea and it basically updates the existing project to match the one I'm importing including edits, selections albums etc.

So instead of creating 2 projects and one new library (under Aperture 2) and having to manually delete the old project after importing the updated on, all I create now is one new library and the rest is taken care of by Aperture. Using this feature with managed libraries (as I always do) works so well. For anyone who hasn't tried managed libraries I urge you to try as in my opinion the list of pros for this just keeps getting longer!

This is one f those small features than would barely make the list of 200 but for me this is saving me huge amounts of time and HD space and is a great feature. Every day I'm finding that some of Apertures less marketable new features are the ones that are making a massive difference to the way I work and making Aperture an even stronger product.