• deep code refactoring
• DOM.extend and DOM.mock were moved to $Document.prototype
• critical bug fix for IE8's innerHTML hook
• drop experimental $Element#context

• critical bug fixes in $Element$define for IE8
• introduce new methods $Element#empty and $Element#value (thanks to @nateroling)
• major improvements in $Element#context implementation
• various enhancements in internal infrastructure

New features

• DOM.requestFrame and DOM.cancelFrame to work with animation frames
• DOM.format supports functions in template strings for advanced formatting
• DOM.emmet encodes values inside of back ticks, so they are always safe
• new $Element#map to invoke function on element if the element exists
• introduce $Element#context (experimental)
• DOM.importStyles now supports at-rules too

API improvements

• CSS accessor module was rewritten - now you can use $Element#css for SVG properties too!
• major performance boost for declarative animations: no forced layout before animation
• visibility methods now don't touch display property to avoid unnecessary layouts
• DOM.importStyles supports only string as the second argument
• the first argument for $Element#clone is required (standards-based behavior)
• drop $Element#defineProperty because it's useless
• rename $Element#defineAttribute to $Element.define and now it accepts just two functions instead of the configuration object
• private functions (on*, do*) are deprecated in favour of methods that start with _

• major refactoring of visibility methods
• various performance improvements in visibility methods
• visibility methods process correctly all word and multiple transitions
• argument callback is always async in visibility methods
• $Element#defineAttribute uses lowercased attribute name
• DOM.format can accept non-string values
• more readable compiled code
• fixed legacy IE improvements

API improvements

• DOM extends $Element and wraps document.documentElement
• method renaming: DOM.template -> DOM.emmet, $Element#style -> $Element#css
• visibility methods can apply CSS3 animation on an element
• update class manipulation methods to match the spec
• new $Element#defineProperty and $Element#defineAttribute
• new DOM.format for string formatting
• new DOM.constructor for getting wrapper for a native element
• style hook for getter/setter
• handler arguments support access to event arguments via numeric values
• handler arguments pass non-numeric and non-string values through
• smart quotes (back ticks) in DOM.emmet
• title hook for DOM (should get/set document.title)
• new DOM.noConflict to safe working with several versions of the library
• move i18n methods into a separate project better-i18n
• version constant on $Element-level
• DOM.importStyles doesn't fail on invalid selectors
• $Element#toString returns "<a>" not "a"

API cleanup

• *All methods return real arrays instead of array-like objects
• argument selector is a separate string in $Element#on[ce]
• drop deprecated DOM.ready: use DOM.extend instead
• drop $Element#legacy: use [0] instead
• drop deprecated $Element#data: use $Element#get instead
• drop $Element#parent: use $Element#closest instead
• manipulation methods support only single argument, Array.<$Element> is acceptable
• drop andSelf argument from traversing methods
• late binding support was removed from event handlers

Infrastructure

• ES6 transpilers for modules and source code
• migrate to gulp
• better jsdocs template
• sauce labs for automated testing on different environments

Improvements:

• custom builds support
• introduced better-dom-legacy.js which isolates some IE8-9 specific fixes from other code
• animations do not require setting display property in CSS
• various syntax improvements in the Emmet parser
• variables in $Element.i18n and Emmet strings have {varName} form (no dollar prefix)
• arrays can be used to specify variables in $Element.i18n or Emmet strings
• $Element.show, $Element.hide, $Element.toggle accept optional callback argument to catch the moment when animation ends
• DOM.extend supports optional argument condition which allows to skip feature detection in tests
• DOM.extend does not mix methods that start with on or do into an element interface
• $Node.dispatch for making safe calls
• DOM.mock accepts optional variables for an Emmet abbreviation
• $Element.get, $Element.data, $Element.style support array argument to retrieve several values
• $Element.next[All], $Element.prev[All], $Element.parent support optional andSelf argument
• pointer-events:none is applied inline to prevent accidental actions during an animation
• $Element.matches supports special :visible hook (which is reverse of :hidden)
• toString returns a lowercased tag name of the element or empty string
• improved API documentation: added modules section, used better template
• update es5-shim version to the latest

Performance:

• $Element constructor should be faster
• use querySelectorAll instead of matchesSelector for testing an element during event delegation except Webkit-based browsers because it's faster

API cleanup:

• extract $Elements constructor for collections
• event handlers accept ["target", "currentTarget", "defaultPrevented"] by default
• currentTarget is used instead of target to find the element that matches event selector
• $Element.toggle accepts the same arguments as $Element.show and $Element.hide
• drop context argument from $Node.on, $Node.once, $Node.off - use Function.prototype.bind instead!
• DOM.extend does not support constructor function as the second argument
• $Element.child does not support optional argument selector

Bug fixing:

• various bug fixes in DOM.extend
• $Node.once works properly with late binding
• DOM.template handles boolean attributes properly
• DOM.template does not cache abbreviations that have the varMap argument
• fix reflow problem in IE8 on attribute change
• Android 2.3 specific bug fixes
• $Element.clone works on empty elements
• $Element.i18n works for collections

Improvements:

• used browserify with node.js-like syntax instead of hacky AMD for module system
• $Node.fire returns !defaultPrevented
• $Node.fire supports multiple extra arguments
• $Node.on: event properties array moved to the end of the method signature
• $Node.on: "detail" event property returns native value instead of event data
• $Node.on: event type could be an array
• $Node.data: object notation syntax is supported for data attributes
• $Element.clone supports optional deep argument
• $Element.set, $Element.style, $Element.toggle accept functor that has (el, index, this) arguments and global context
• $Element.show, $Element.hide support optional delay argument
• revised i18n: no *en.js files anymore - english strings are used as resource keys
• $Element.i18n: variable syntax is consistent with DOM.template
• add textContent hook for IE8 via innerText
• DOM.template supports variables in abbreviations
• DOM.extend doesn't expose event handler methods (/^on[A-Z]/) into element interface
• DOM.mock exposes event handler methods into element interface

Performace:

• $Element constructor is faster
• DOM.template supports memoization of results
• SelectorMatcher has optimized support for [attr=value] selectors
• improve $Node.on by reducing function calls and earlier cancelling in case of event delegation
• lot of different performance optimizations in DOM.extend and DOM.create

API cleanup:

• drop DOM.watch because of incossistent behavior in different browsers
• drop $Node.supports: use $Node.legacy for feature checking instead
• no more : operator support in emmet abbreviations - use [type=xxx] instead
• DOM.create accepts optional emmet variables object instead of attrs and styles
• drop $Element.width and $Element.height - use appropriate properties of the object returned by $Element.offset

Bug fixing:

• DOM.extend works properly with DOM.ready
• DOM.create doesn't wrap collections with extra div
• DOM.data doesn't throw exception
• manipulation methods work properly with detached elements
• traversing and searching methods return empty node at least
• various fixes of default styles for [aria-hidden=true]
• fix DOM.importScripts in case of single url with no callback
• $Element.style sets composite css properties correctly

Improvements:

• $Element.set(value) accepts primitive types and function
• DOM.importScripts can be used to load scripts one-by-one
• $Element.on now fixes target property: the element always matches event selector if it exists
• introduce $Element.width() and $Element.height()
• it's possible to cleanup style value using $Element.style with null, undefined or empty string
• add CommonJS modules support
• main files moved into the dist folder
• change jsdoc template

API cleanup:

• getData/setData were renamed to data
• getStyle/setStyle were renamed to style
• DOM.parseTemplate was renamed to DOM.template
• $Element.unsafe was renamed to $Element.legacy and respects current context

Bug fixing:

• DOM.create and manipulation methods now trim HTML strings
• DOM.watch and DOM.extend allow to catch the same element via different selectors
• manipulation methods don't fail on an empty string