I am going to assume people that need this can find the menu items themselves so I am not going to repeat the documentation. I am also not going to walk through every combination of possible work-flow and connect all the dots that can be connected. I will leave that for the Aperture 3 File Management eBook update. Instead I am going to give a couple observations that maybe helpful after beating Aperture 3 over the head with some of my work-flows.
In a nut shell the new functionality is fantastic. I love that any combination of objects you select in the project inspector works. I love that you can open each exported thing as it's own library. I love how smart it is in dealing with combinations of referenced and managed images. I love how it deals with off-line images. It for the most part works as you would expect, maybe even better. Apple did a great job covering the needs of just about everyone no matter how simple or complicated what you envision it should be not only possible but easy or easier than it was. The key to using this and having it work the way you really want it to is the judicious use of the consolidate and include preview checkboxes. You can make just about anything happen between multiple computers, libraries, whatever.
First - you are perfectly fine if all you do is add new big objects in multiple libraries. Big objects being albums, books, etc. You are also fine modifying the contents of those objects like adding or deleting images from those things or modifying book pages. If there happens to be conflicts Aperture asks you which library takes precedence when merging. You get this choice once on import - not project by project or item by item so beware. If it does not ask you then there are no conflicts. Well almost - I have been able to create conflicts with individual image items that have gone undetected that just disappeared but I tried hard.
File status for master files (referenced/managed/off-line, etc) is completely independent for each library and works just like it should. Example - if you export a project from your main library that has referenced masters using the consolidate masters checkbox and import it on your laptop - everything works fine. If on your laptop you relocate those masters to somewhere completely different and then import that project back to your main library everything for both projects stays the same and works just like it should. Why would you want to do something like that? Well… How about sharing projects between computers and speeding up the transfer to sync them by NOT transferring the masters every time. No matter whether it is a computer in the same room or across the world this speeds common images/project transfer up a lot - especially if you choose NOT to include previews. I had a work-around for Aperture 2 but this is much faster and easier. Heck all of those associations are image master by image master so you can do all sorts of nifty things.
One might be a shared project with those masters that you work on on the road and at home. You could also select your 5 star smart album for your entire library as a separate export even if they had overlapping images. In the first export you consolidate masters and do not include previews. In the second export you don't consolidate masters but include previews. When you import both into your laptop library you can relocate the masters for that shared project so they will never transfer again. You will also have previews with off-line masters for all your 5 star images that you can share with iLife on your laptop. It doesn't matter that some of those have masters and some of them don't. When you ship the project back to your main library everything will be just fine when you merge. Very cool - completely independent file status per library. Go wild any selection can be exported using this do a couple of different exports some with masters some without. Some with previews some without - go wild.
Now about adjustments to images that exist on both machines. The short answer is only adjust image versions on one machine at a time before merging the changes. If you must do it on both machines to the same set of images do yourself a favor and make a new version when you do. Even this has it's drawbacks - I don't know if it is a bug and will get fixed or that is just the way it is. Heck it could be my Aperture 3 installation at this point but here is what happens even if you don't make new adjustments of both machines - let's say some new versions.
Say you had a couple of albums that contain those image versions already. You create a new image version on your laptop and ship it back to your desktop. That version will show up in the stack at the project level but… it will not be in the stack in the albums that already existed for that stack. No this is not a feature - in fact the album will show the correct number of images after everything is merged but when you open it in any album that existed before the new version was created on the laptop you will NOT see the new version. Not earth shattering but definitely confusing considering stacks are stacks. This could have serious consequences to your work-flow and overall organization scheme. The image at the top shows this if the words are not clear - also note the version names!
On another note - even if you move masters back and forth with completely consolidated managed libraries projects etc. Changes to the master files are NOT picked up in a merge. For instance write metadata to the masters for a project that already exists in two libraries and then merge them the library that you DID NOT write the metadata to will still not have the metadata in the masters. Get it? Again not a giant deal just be aware in your planned work-flow.
By the way you do not have to drag and drop one library onto another to import/merge there are a million ways to do it - file import->lbrary/project, double clicking a different library while Aperture is open with a different one, etc. That is probably obvious but just wanted to put it out there.
Hope this helps some of you that have large libraries and sophisticated multi-computer workflows.