The team behind WordPress.org has launched a brand new, and improved, theme directory experience.
The directory also goes into a customizer-like experience when you click to preview a theme.
My one beef is that I wish the demos themselves could be customized by the theme author to create a proper demo, and not the auto-generated one from WordPress. I know that would be ripe for abuse, but maybe there could be a way around it.
Either way, the Meta team deserves a round of applause. This is a superior experience to the old setup by far. You can view all the archives of what went into this by following this tag on the Meta blog.