I haven't had an issue with posting yet - I've switched to chrome. I welcome the change. But I agree with the others about white space. The line spacing is a bit too much. Sure you can zoom out, but it doesn't change the proportions - just makes the font smaller. The old software had a denser line spacing, enabling you to see more posts on a page with the same zoom setting as before. It would be nicer to keep the line spacing the same as it previously was.
The other thing is on the forum summary pages (not thread detail) they've included everyone's Avatar, which eats up vertical space. They have a setting at the top "Full Version" and "Essentials only" which is nice - however the avatars still show up with Essentials Only. Maybe they should tweak the Essentials settings to give a tighter line spacing and get rid of the avatars on the main Forum summary pages.