A couple of people in the forums relied on the old Overview functionality and I've open up two requests on their behalf. Since 4.1 is still relatively fresh and there's not too many complaints yet, but I'd expect more questions on this as users get familiar with 4.1. I'll point them to these two issues to vote up, so we can gauge popularity a bit better.
CHD-1139 [Overview] Bring back the list of 'Waiting' buckets for each group on the sidebar
CHD-1143 [Overview] Bring back the option of not showing 'Assigned' tickets in the 'Open' section of the sidebar