The HTML5 spec greatly improved the automation of the outlining algorithm and as such browsers and screen readers will definitely benefit by your inclusion of html5 tags and ARIA roles.
Mozilla produced a great document on this topic that addresses the incorporation of html5 elements into that of an html4 document. This should serve as a great example of where you can swap out some divs for more semantic elements. Found here: https://developer.mozilla.org/en-US/docs/HTML/Sections_and_Outlines_of_an_HTML5_document
With that said, the new semantic elements of HTML5 do capture a lot of the div's territory, but the div should still be used when there is no other semantically appropriate element that fits your purpose. This has also been greatly expanded upon by html5 Doctor. Found here: http://html5doctor.com/you-can-still-use-div/