This lay-out looks really messy. There's a bunch of stuff that just doesn't make sense. It might be my resolution, but the cards are each of a different size, don't neatly center, and leave a huge amount of white room between them. I can't find the pattern as to why the cards are spread out so weirdly. I'll include screenshots below.
The fact that subforums are not visible is a huge mistake. It makes navigation more difficult and hides a lot of the content some subforums offer. Especially for sections like the roleplay theater, it's counterintuitive.
The data being displayed is also annoying. For example, if scrolling down to the City Hall, it looks like this topic is called Homepage Layout Today, instead of Homepage Layour, with the last post being made today.
I also agree with Seeker, in that it's really weird that this is being done live for all users. An easy opt-in at the top of the page seems like a better option to me.
Images of weird sub-forum cards:
EDIT:
Just actually went into a sub-forum instead of a thread. The fact that sub-forums are above the header is not ideal. For example, entering the RPT with the intent of checking on a roleplay thread, I'd have to do a weird illogical scroll up and down to check if there are new posts in the main forum. They sub-forum cards are also really big, and kinda take up an unnecessary amount of space. The header combined with sub-forum links are taking up my whole screen already, and there's not really any content being displayed.
The main page also displays if the thread in the preview has unread messages, but this isn't a thing for sub-forums. I'd love to see something indicating that. I liked how the classic layout did it, with the big icon displaying that info. The images at the front are fun, but the fact that they take up a lot of space without actually serving a purpose makes them a bit obnoxious.