The first one I noticed is there's no animated GIF's visible as our avatars (SURE you can click on the avatar and see it animated in the little info box thing but that kinda defeats the point.)
The size of it doesn't bug me as much. I already had to resize stuff or look for a smaller copy to be able to upload before. It's just the fact that it's NOT MOVING that bugs me.
I, too, miss having the list of those reading the current thread available.
I haven't noticed the top 20 or all online users lists yet but I'm sure I just have to look some more (not that they're really important but just something I looked at when I was REALLY bored.)
"friends" sounds better than "followers". It sounds 2-way and ... just nicer.
It was nice having the drop-down menu from our name always visible on the screen.
THE BIG ONE FOR ME
I liked being able to just click on "my content" in that user-menu and be able to see all the THREADS I've posted in. Right now it just shows a list of POSTS. (with threads I can see the little circle next to the ones that have new, unread content.) I used this feature a lot. If it's still there somewhere, could someone PLEASE explain it to me or a workaround until it's fixed. I'd greatly appreciate it.
/complaints
EDIT : Also, almost forgot to mention that the multi-quote thing was useful sometimes.
/complaint edits.