Hi Mark,
1) What I dislike and improvements:
1.1 - What I miss the most is a "list all recent topics / list all latest activities" menu link (the previous design landing page). It was nice to see all activities and find interesting topics you would like to read or join, now you have to browse and browse and browse that is really not user friendly!
1.2 - 10 topics per page in the subcategories is not enough 20 would be better or let the front user decide the list lengths, e.g. a small dropdown selection list 5,10,15,20,25 per page.
1.3 - In small screens the columns are not nicely rendered. The topic name column is very (too) small and the posting time column is too large. If possible I would prefer to "merge and stack" the first two columns eg for smaller displays: 3 main columns instead of 4, the first column stacks the topics title and under the title the posting time, then second and third columns posted by/Last replied.
1.4 - Approximately at tablet size window the vertical separator line between the menus does not touch the bottom border if the menu title is not 2 lines (Bookmarks/Subscriptions)
1.4 - The toolbar is not responsive, Subscriptions and Edit Profile disappear
2) Considering ED 4.0
2.1 - The colors and icons look great. Will the admin be able to set the images / icons font set themselves for container categories/categories/topics...?
2.2 - A nice feature would be the possibility to choose a background color for the categories header (one by one in the specific category creation/edit page)
2.3 - Maybe a toolbar like ES1.4 would help to have a clean and consistent design. English terms are usually small words but other languages use more characters or even 2 or 3 words to say the same...think about it please.
These are my first impressions, others may come later