The main navigation and theme is largely the same, but links have been re-ordered,
usability had been improved, and there is a splash of Ajax in the beta. The first noticeable change is in the right sidebar, which has been cleaned up and segmented better. Note that on both versions, Google search now takes a prime position in the center of the page. You can also sign in to YouTube with your Google account, although this remains optional for now.The new version has specific sections for 'Related Videos' and 'Promoted Videos' (a.k.a. popular ones). The 'Director' videos have been cut, perhaps reflecting that popular videos aren't necessarily professionally made by a director. At first glance it seems odd to cut the 'More from this user' section, but I think this has been integrated into 'Related Videos' (as with 'Playlists'). So YouTube has reduced the number of clickable options, by consolidating them into one section.
Friends would like to know your views as well on this new beta, post in you commensts below...