*`TableListField`, `ComplexTableField`, `TableField`, `HasOneComplexTableField`, `HasManyComplexTableField` and `ManyManyComplexTableField` have been removed from the core and placed into a module called "legacytablefields" located at https://github.com/silverstripe-labs/legacytablefields
*`prototype.js` and `behaviour.js` have been removed from the core, they are no longer used. If you have custom code relying on these two libraries, please update your code to include the files yourself
*`Object::has_extension()` and `Object::add_extension()` deprecated in favour of using late static binding, please use `{class}::has_extension()` and `{class}::add_extension()` instead, where {class} is the class name of your DataObject class.
* Removed `SiteTree.MetaKeywords` since they are irrelevant in terms of SEO ([seomoz article](http://www.mattcutts.com/blog/keywords-meta-tag-in-web-search/)) and general page informancy
* Removed `SiteTree.MetaTitle` as a means to customize the window title, use `SiteTree.Title` instead
* Removed CMS permission checks from `File->canEdit()` and `File->canDelete()`. If you have unsecured controllers relying on these permissions, please override them through a `DataExtension`.
* Deprecated global email methods `htmlEmail()` and `plaintextEmail`, as well as various email helper methods like `encodeMultipart()`. Use the `Email` API, or the `Mailer` class where applicable.
*`FormField->setDescription()` now renders in a `<span class="description">` by default, rather than a `title` attribute * Removed `Form->Name()`: Use getName()
* Removed `FormField->setContainerFieldSet()`: Use setContainerFieldList()
* Removed `FormField->rootFieldSet()`: Use rootFieldList()
* Removed `Group::map()`: Use DataList::("Group")->map()
* Removed `Member->generateAutologinHash()`: Tokens are no longer saved directly into the database in plaintext. Use the return value of the Member::generateAutologinTokenAndHash to get the token
* Removed `Member->sendInfo()`: use Member_ChangePasswordEmail or Member_ForgotPasswordEmail directly
* Removed `SQLMap::map()`: Use DataList::("Member")->map()
* Removed `SQLMap::mapInGroups()`: Use Member::map_in_groups()
* Removed `PasswordEncryptor::register()/unregister()`: Use config system instead
* Methods on DataList and ArrayList that used to both modify the existing list & return a new version now just return a new version. Make sure you change statements like `$list->filter(...)` to $`list = $list->filter(...)` for these methods:
*`DataList#dataQuery` has been changed to return a clone of the query, and so can't be used to modify the list's query directly. Use `DataList#alterDataQuery` instead to modify dataQuery in a safe manner.