Arranging by activity will show you anything new - either new posts, or posts that have just received a new comment.
Formatting help is also embedded now. Just click "formatting help" when you're making a new post and it'll show all the markdown options you can use without loading a new page or taking you off-site.
There have been big performance upgrades under the hood so the site should load even faster than before.
Give your thanks to u /u/emma by donating.