8.0.0 8.0.0 (beta)

This release represents a huge step forward for Preact:

Significantly increased performance - in some cases by 30%.
Better compatibility - key for PFC's, class integrations, capturing events.
Fewer edge cases - goodbye to unnecessary mounts and DOM hierarchy errors.
Even smaller - Preact had been 3.9kb for a while - now it's 3.3kb (and headed for 2.9kb!)

💁 If you're looking to upgrade, be sure to read the quick guide.

Breaking Changes

Pure Functional Components now have backing instances. This means key now works perfectly on PFC's. It also means you could use state and lifecycle methods in Functional Components... (#163, #517, #536, #586, #474)
linkState() has been removed from Preact itself. It is being published as a standalone linkstate module shortly.
class and className no longer serialize Object values to Strings. Instead, use classnames (#401)
preact/aliases is no longer necessary. createElement() is now an alias of h() right out of the box!
DOM element recycling has been removed. It was a source of issues for many, and is no longer necessary for great performance thanks to diff optimizations that reduce the number of cases where elements are removed and re-added. (#544, #351, #461, #459, #503, #535, #562)
Undefined components references now throw rather than rendering <undefined> (#574)
No more Symbol. Instead of try to use Symbol.for('preactattr'), __preactattr_ is always used.
Render debouncing now uses setTimeout(0) instead of Promises. It's smaller, doesn't swallow rendering errors in Safari, and was already the fallback (#357)
The non-standard componentDidUnmount() lifecycle method is removed. Use componentWillUnmount().
onXxxxCapture is now supported for registering capturing event handlers.
Events like focus and blur are no longer automatically capturing by default.

Hierarchy errors are a thing of the past (thanks to recycler and PFC rewrites) (#380, #391)
Fixed edge case that could cause children to be rendered out of order (#581, #603)
Unmount lifecycle is always fired when replacing a Component with an empty element (#538, #534)
ref functions attached to DOM nodes are no longer invoked for updates, only for mount/unmount.

"holes" in JSX children are now preserved and used intelligently by the diff (#580, #540)
Re-rendering a compositional child with a different key prop now triggers a remount (#338)
JSX children passed to a Component are preserved rather than normalized (#551)
Preact no longer relies on the Text or Array constructors for type checks, instead relying on duck typing (#595, #530)
Ignore whitespace-only Text nodes during SSR hydration. SSR boot is now significantly faster than cold boot.

Here's the list of changes itemized by commit:
master...8