The first thing I noticed is what fmk pointed out. You can't go directly from the thread link on the forum to the last page. I appreciate that you can apparently go to the first unread post (I haven't tried that), but if a thread has been really busy since I last browsed it, often I just want to go to the last page to get an idea of what's going on. Then I can make the decision whether to go back and look at some of the preceding unread posts.
There is another forum I frequent where they do the same thing, and I always liked CN because of the ease of going to the last page of any thread. For sure, I never want to go to the first page of any multi-page thread once I've read the first post.
I think only showing the most recent post quoted is very helpful. In the past, lazy people have quoted a long list of previous posts, which IMO logs up the forum. Granted, sometimes it's easier to follow a discussion when you see a string of posts all at once, but too often we would see the same string repeated again and again, with one short new response each time. So I think the new system is better.
I haven't yet seen how threads that have had activity since I last opened them are distinguished from ones that haven't. From reading this thread, I take it there is a difference in color, which I will have to check on. In another forum I frequent, newly active threads are shown by being bolded, so one can tell in a glance.
I also see that after starting this post, and not wanting to post it yet, I can go back and look at other pages in the thread without losing what I've already written. That is a big plus. I tend to modify posts on the fly, as I acquire more information, and this is a big plus.
On the whole, I'm having a little trouble with the new format, but that may be just a matter of time getting used to it.