The average theme design now only uses 8 external JavaScript files instead of 11
Several resources (such as Custom CSS) will now be cached by the web browser for up to one year or until they are next modified (whichever is sooner)
Theme layouts contain much more intelligent caching on the server to reduce processing time
We've waded through the Java, HTML, JavaScript and CSS with all manner of diagnostic tools and made huge numbers of small improvements throughout the plugin