Still have to play around with it to see what its like, but have some cosmetic comments. Granted, I understand this is a test forum and by no means final, I figured I'd share just for consideration and discussion.
1. Please list subforums under the main titles. Its hard to browse when there are only 4 items with the subforums listed under them. Forum looks tiny and hard to navigate. The current style where subforums' subforums are listed like that but the main subforums are laid out is better.
2. Please please please have a "disable mobile view" option. I just pulled up the forum on my phone and just like vB5, there is no way to disable mobile view and that really kills the site for me. If you want a mobile friendly experience, use Tapatalk. I use Safari to have the full site because I don't like the simplified interface (and I'm not the only one).
3. Full width forum would be nice. Those sidebars with "latest posts" and "latest profile posts" don't add anything to the side and just take up space. My screen is 1920px wide, but the actual forum part is only 910ish px wide.
4. Not enough new posts to properly test this, but it seems like the "go to new post" feature is just as bad as it is on vB5.
Not to be a Debbie Downer, but sadly I'm not seeing this as an improvement over where the forum is now usability wise. I know it won't happen, but I do really wish we could go back to vB4. Are there really no security patches to make it safe?