Tabs was a feature I was keen to get my hands on in this version. However, it does not appear to be working correctly.
Doing some testing with 2 tabs main and location.
I am completing all fields as if they they where on the one tab but I get these errors
Clicking the save button on the main tab.
ERROR: A validation error occurred in the location tab. Please verify that this tab's input is correct before saving.
Clicking the save button on the location tab.
ERROR: A validation error occurred in the main tab. Please verify that this tab's input is correct before saving.
Appears to have a problem with validation on save but all fields have been filled out. So I moved all the fields which are required fields onto the main tab and left un-required fields on location tab and surprise the record save.
I reversed this: required on location tab and it saved.
Move one required field back to the main tab and error..
So in summary...
1. You cant save if required fields are spread across multiple tabs.
Bug or Feature

Also found that:
2. Tabs do not work/appear under a relationship (all fields displayed as if tabs not used)
Again Bug or Feature?
I will test further and post any more findings in this post.
Paul