We recently upgraded from a 1-year old Jira/Greenhopper to Jira 4.4.3/Greenhopper 5.7.2. One of the things we seem to have lost is a 'popup' view in the planning board, where the full card would open (in a popup with the planning board kind of glassed-out) and be editable as an ajax-y call, without opening a new tab or opening the card page directly.
I don't know what to call the lost mode or how to find it in the new version of Greenhopper, but my users are not happy with this feature missing.