When I decide that I want to subscribe to a thread, I am at the bottom of the postings in that thread, cumbersome to first scroll up and then have 3 clicks to subscribe to that thread... Please make available a one-click link on the end of each screen of messages. If a posting has more than one page of messages in the thread, each page should have a one-click subscription link at the bottom.

Even "QuickLinks" are two clicks away..! (more than room enough to put them out in the open, not behind a drop-down menu)

Having the who's online list at the bottom, especially when being on the front page refreshing the page every now and then, it gives less of a active community / presence feeling. Please move that part back on top of each page/screen, and what about giving the users the possibility to set an automatic refresh rate (in minutes, up to at least 60 minutes). Note that if a user is typing something in a text box like here in the postings section, make sure that a refresh does not loose the text that was not saved yet...)

Where is the previous quick "Search this forum"...?!

In general, the new design gives an impression that tidiness of interface (neat menues etc) has had priority over efficiency of those who are beyond the phase where they are exploring the interface. That is discouraging. It is even more critical to have one-click options in a busy forum where time gets even more critical as one cannot keep up with it all...
Not a good idea to leave active users with considerations of whether to check out another forum or not just because efficiency is difficult or "impossible".

There are of course several improvements, though, I am not all unhappy.

However, some of the options that are now cumbersome are critical to the feeling and inspiration of using the site. Psychologically appropriate colors for such an (active) collection of forums, the feeling of efficiency and actually easily finding what you seek are examples of critical features. A clean interface is important, but don't waste space...