The beta theme has been expanded and promoted to the big show. At the bottom of every forum page you will find the theme chooser with S, M, L and XL size themes all in both light and dark versions.
M is the new default size but if that's too small for you, the L size is the same font size as the previous theme's font size.
If your browser is giving you guff with any missing bits, you just need to clear your browser cache (try a simple shift+reload/shift+f5 first) or you could try switching to a different theme and back to what you want.
If you find any bugs please post them in the Bugs forum.