Again this is likely due to template and css edits.
Create a new default style with no parent and if the problem is no longer apparent then you will need to look at your templates.
Check in the navigation templates.
I noticed that as well, and as Brogan said, probably a custom template issue. Since they just released it, I'd give it a few days before raising hell. It's not like the big "login" button is missing
The space between the Tabs is due to the Navigation template needing to be reverted, and was not listed as being outdated. The issue for not having all outdated templates listed isn't new to Beta 4, but was discovered.
Agreed i love XenForo and the mods and developers do their best, like VBulletin they have about 500 errors on one release, a few errors cant be that bad can it?