You are correct that the Acrobat X Family does not display Acrobat 9 PDF portfolios in the same way - it will respect the navigator embedded in the file but will use the new triple-mode method of displaying content, where clicking on a file thumbnail opens the document in Read Mode and access to the full content requires the file to be opened separately via the button on the right of the toolbar.
If a PDF portfolio created in Acrobat 9 has a welcome screen and/or a header, these WILL display in Acrobat X and Reader X, at least until you dismiss the welcome screen with the "Don't show again" checkbox.
The creation of PDF portfolios with welcome screens and dynamic content in headers (SWF files, links, etc) has been removed in Acrobat X.
This week I'm hosting a webinar on how to use our free Adobe cloud (i.e. Acrobat.com) with Adobe Captivate 5 as a lightweight Learning Management System (LMS) for publishing and tracking Learners' Quiz Results.
Wealth of Information including proper setup within MS Office documents in order for Acrobat to read fields properly.