I really like what's happening with themes and styling in DM. Creating custom look and feel has become much easier in the latest release. With pages, flavors, and CSS styling comes a flexibility that henceforth did not exist in DM. Styling has become another configuration item, rather than a mystical journey into big and ugly XML file requiring a modicum of magic to get the result you wanted.
I was a saddened a bit to see this new approach hadn't propagated through to DAM. When I went to perform a comparatively simple branding task in a Nuxeo deployment with DAM and DM I found the 'flavor' extension point only applied to DM... So the following XML, which I thought would change the logo in all places only showed up in the DM UI.
<extension target="org.nuxeo.theme.styling.service" point="flavors">
<flavor name="mybranding" extends="default">
To get the logo to change in DAM I had to revert back to pre-5.5 approach. Easy enough change once you realize what's going on, but slightly confusing at first when your logo insists on not changing.
I know this will eventually be rationalized. I just hope it's sooner than later.