OK so this new forum software has some cool new things, here are some:

Automatic comment display - If you're in a thread, you don't need to refresh to see new comments, they will just appear. This bridges the gap between a chat room and a forum.
Attachment thumbnails - If you attach an image it will automatically make a thumbnail, and provide a link for putting the full image in the post if you want.
Categories as filters - With the categories on the right hand side they act as filters instead of having to go to a different page to change category.
Private messaging - You can send private messages between people, and you can add as many people to each conversation as you want, like communal private messaging.
Activity - The new activity page ties in with profiles to let you post status updates and stuff like that.
Save draft feature - You can save drafts of posts (and they are automatically saved too) which means if your browser crashes or you just want to go away and write it later, you can do that easier.