There's been an interesting discussion on the jQuery-a11y mailing list about the different styles of keyboard interaction for Tabs. We should modify our jQuery UI Tabs demo to illustrate these styles.
I'll see if I can summarize the two
1. As per the style guide, a tab should be selected immediately upon
being focused with the arrow key.
2. Tabs should not be automatically selected when they get focus. The
user should be able to explore the list of tabs with the arrow keys,
and then press Enter or Space to select their desired tab.
There are a few factors to consider when choosing one or the other. If
you check out tabs on your desktop OS, you'll find that they behave
differently between the Mac and Windows. Windows uses style #1, while
the Mac more or less uses style #2.
The other issue that you mention is AJAX. If the contents of a tab are
loaded dynamically upon selection, it could be quite tedious for the
user if they have to wait for each tab to load as they cycle through