There are a lot of problems with the button bar. Here are 2 problems:
1. What is the point of button bars, if they can't be used for simple functions like going to the next record? Sure, you COULD use the button bar to go to the next record, but VISUALLY it doesn't work because the button you just pressed always stays "active". There is no way to make an active button immediately inacitve so the hover state works again on that button when you hover over it again. (We're forced to revert back to normal buttons -- can't use the button bar.)
2. Can't copy & paste any styles for any parts of the button bar. Please see attached screenshot.