There doesn't seem to be a collated feedback thread on here, so I'm going to tack my response on to this one. Copied and pasted from the official Sims forums:
At the moment, I don't like the new forums. And I'm not just resistant to change! I'm just resistant to bad design.
1) No custom avatars except for certain ranks. Yes, I know that it's "being looked into". But that means it's not a guarantee. The fact that you chose a forum style without first ensuring that users would all be able to choose an avatar is really telling. This should have been a bigger priority, because nothing makes me feel less welcome on the new forum than you taking away a feature I had here and telling me that only your chosen ranks get it now. This should have been looked into and set up before you launched.
(As an aside: I don't really want my EA account avatar for the new forum. I chose a Sims-related avatar for a Sims-related forum.)
2) Nested replies makes finding new responses harder. I read a lot of threads, and I appreciate that I can read them in chronological order. Having to jump back up to nested replies - on the off chance that there is something new - makes reading through the flow of a conversation incredibly difficult.
3) "Show More" instead of page numbers is a pain to load. My browser will eventually give up on loading if a thread gets to be too long. If I can't load an entire thread, I can't read it.
4) Forum posts are small and hard to distinguish from each other. On this forum, avatars are big and I can quickly tell when I'm finishing one post and starting another from a different user. On the new forum, I can see when someone has finished their comment, but all of the posts feel more "collapsed" and it's a lot easier for my eyes to slip over posts without fully taking them in.
5) The new forum feels cluttered. When I read a thread on here, my eyes are drawn only to the posts/replies in the specific thread. On the new forum, the sidebar of related posts/recent discussions ends up drawing my eye and makes the browsing/reading experience less enjoyable.
I was actually expecting the new forum to be closer to the Answers HQ style, which is - bizarrely - a bit more like this forum. Posts are more distinct, avatars are large and noticeable, browsing is done through page numbers. The biggest issue for me with the Answers HQ style is that the posts column is too thin, like it was designed for viewing on a phone (which feels a bit silly because most of EA's games are probably played on PC or console).
The new forums feel frustrating to participate in. They feel oddly devoid of character, and easy to ignore, like when you see a bunch of example posts on a blog that are written in Latin. It does not feel like an upgrade or even a pleasant side-grade experience.