There are lots of exciting new features rolling out in Safari 9.1 such as support for the picture element, enhancements to the web inspector, CSS variables and gesture events for iOS. Although, what I’m most excited for is the OpenType support with properties such as font-feature-settings and its variants like font-variant-ligatures and font-variant-caps, all of which give us more fine-tuned control over typesetting.
You can play around with these new features in the OSX 10.11.4 and iOS 9.3 betas today.