Any value in exporting iPhoto pictures and importing them into Aperture?

Just in case you have not come across these:

Aperture 3.3: Using a unified photo library with iPhoto and Aperture

Aperture 3.3: How to use Aperture to merge iPhoto libraries

but I am wondering if there is any value (or even if it is possible) to export all of the iPhoto pictures and import them into a new Aperture library?

You can - an it will depend on what you want to achieve, if that will usefull. The way to do this would be by imprting your iPhoto library into an Aperture library using Aperture. But Aperture libraries and iPhoto libraries are now interchangable - both are photo libraries, and you could simply use your iPhoto library in Aperture and be done now.

Some reasons why you would want to turn your iPhoto library into a library recognized as Aperture library by importing it into a new, empty Aperture Library:

• As long as the photo library will have the "Kind: iPhoto library", you will have to upgrade both iPhoto and Aperture always to the newest versions, or you will not be able to upgrade to a new library format, when a new release of Aperture comes - say (iPhoto '12 and Aperture 4); you will probably have to buy both new releases to continue working with your iPhoto Library in Aperture.
• If the kind of your library is "Kind: iPhoto library", it will appear in the Media Browser in the iPhoto section, not in the Aperture section, even if you are using it as your Aperture library. And before syncing with iTunes you will always have to open the Aperture library in iPhoto to point iTunes to it.
• Also, in Aperture you have more control about what will be included in your library - In iPhoto there is no way to specify the size and quality of previews. If you do not want or need previews, or you want smaller previews, or no Faces, it would make sense to recreate your iPhoto library by importing it into a new, empty Aperture Library.
• If you have more than one iPhoto Library, you can merge them into one big Aperture library to be able to browse all your images without having to switch between libraries. Aperture works very well with really big libraries. There is no need to split libraries.

The reason that I'm asking this is that I know there are a lot of duplicates in my iPhoto library and I know that Aperture keeps only the original.

That is what I meant by having more control on what will be stored. iPhoto will always store a very high quality preview of your edited version; in Aperture you can decide what the preview size and quality will be. But Previews and originals are not duplicates; they are not the same image.

Regards

Léonie

if there is any value (or even if it is possible) to export all of the iPhoto pictures and import them into a new Aperture library?

It's certainly possible (that's what you can do wit File -> Export in iPhoto) but if you do what do you lose? That will force you to choose between the Original (in which case you lose your editing work) or the Edited version (in which case you lose youe Master and non-destructive editing) and there will be no way to get all your metadata over - depending on what you choose.

The reason that I'm asking this is that I know there are a lot of duplicates in my iPhoto library and I know that Aperture keeps only the original.

Aperture keeps the Original. So does iPhoto. Aperture (unless you decide otherwise) generate a Preview, so does iPhoto. Both generate thumbnails. If you use Faces both generate thumbs for that. So unless you decide to not generate Previews (and thereby remove all the integration with the OS, like easy emailing and uploading, sharing and so on) they both work 99% in the same way.

For dealing with duplicates in iPhoto check out Duplicate Annihilatoror Decloneror iPhoto Duplicate Cleaner