I just upgraded from Kibana 4 to 5 and was quite disappointed by the new L&F of the dashboard. The dark theme especially looks very ordinary compared to the sharp look with borders around each visualization that was in Kibana 4.0. It's also pretty annoying / distracting to see the dotted borders around each visualization upon doing a mouse over giving the appearance of the dashboards being in development / edit mode rather than something presented as an end deliverable.
I see that the blog announcement specifically mentions that the removal of borders around each visualization as an improvement (https://www.elastic.co/blog/kibana-5-0-0-released)
Oh, and we got rid of those stupid borders. You know the ones we’re talking about. Seriously, who puts borders on widgets in a dashboard? Not us… anymore.
Not sure how others feel but the new UI looks like a step back to me as well. Additionally the collapsed side nav always being visible is also rather distracting and has a color that does not match with the dark theme. Is there an option for a full screen mode for the dashboard alone?