Index: wp-signup.php
===================================================================
--- wp-signup.php	(revision 18491)
+++ wp-signup.php	(working copy)
@@ -213,7 +213,7 @@
 	$meta = apply_filters( 'signup_create_blog_meta', array( 'lang_id' => 1, 'public' => $public ) ); // deprecated
 	$meta = apply_filters( 'add_signup_meta', $meta );
 
-	wpmu_create_blog( $domain, $path, $blog_title, $current_user->id, $meta, $wpdb->siteid );
+	wpmu_create_blog( $domain, $path, $blog_title, $current_user->ID, $meta, $wpdb->siteid );
 	confirm_another_blog_signup($domain, $path, $blog_title, $current_user->user_login, $current_user->user_email, $meta);
 	return true;
 }
Index: wp-login.php
===================================================================
--- wp-login.php	(revision 18491)
+++ wp-login.php	(working copy)
@@ -586,10 +586,10 @@
 
 		if ( ( empty( $redirect_to ) || $redirect_to == 'wp-admin/' || $redirect_to == admin_url() ) ) {
 			// If the user doesn't belong to a blog, send them to user admin. If the user can't edit posts, send them to their profile.
-			if ( is_multisite() && !get_active_blog_for_user($user->id) && !is_super_admin( $user->id ) )
+			if ( is_multisite() && !get_active_blog_for_user($user->ID) && !is_super_admin( $user->ID ) )
 				$redirect_to = user_admin_url();
 			elseif ( is_multisite() && !$user->has_cap('read') )
-				$redirect_to = get_dashboard_url( $user->id );
+				$redirect_to = get_dashboard_url( $user->ID );
 			elseif ( !$user->has_cap('edit_posts') )
 				$redirect_to = admin_url('profile.php');
 		}
Index: wp-includes/user.php
===================================================================
--- wp-includes/user.php	(revision 18491)
+++ wp-includes/user.php	(working copy)
@@ -1566,7 +1566,7 @@
 
 	// Update the cookies if the password changed.
 	$current_user = wp_get_current_user();
-	if ( $current_user->id == $ID ) {
+	if ( $current_user->ID == $ID ) {
 		if ( isset($plaintext_pass) ) {
 			wp_clear_auth_cookie();
 			wp_set_auth_cookie($ID);
Index: wp-includes/capabilities.php
===================================================================
--- wp-includes/capabilities.php	(revision 18491)
+++ wp-includes/capabilities.php	(working copy)
@@ -360,8 +360,6 @@
 	/**
 	 * User data container.
 	 *
-	 * This will be set as properties of the object.
-	 *
 	 * @since 2.0.0
 	 * @access private
 	 * @var array
@@ -378,17 +376,6 @@
 	var $ID = 0;
 
 	/**
-	 * The deprecated user's ID.
-	 *
-	 * @since 2.0.0
-	 * @access public
-	 * @deprecated Use WP_User::$ID
-	 * @see WP_User::$ID
-	 * @var int
-	 */
-	var $id = 0;
-
-	/**
 	 * The individual capabilities the user has been given.
 	 *
 	 * @since 2.0.0
@@ -471,7 +458,6 @@
 	 * @return WP_User
 	 */
 	function __construct( $id, $name = '', $blog_id = '' ) {
-
 		if ( empty( $id ) && empty( $name ) )
 			return;
 
@@ -488,15 +474,43 @@
 		if ( empty( $this->data->ID ) )
 			return;
 
-		foreach ( get_object_vars( $this->data ) as $key => $value ) {
-			$this->{$key} = $value;
+		$this->ID = $this->data->ID;
+		$this->for_blog( $blog_id );
+	}
+
+	/**
+	 * Magic method for checking the existance of a certain custom field
+	 *
+	 * @since 3.3.0
+	 */
+	function __isset( $key ) {
+		return isset( $this->data->$key );
+	}
+
+	/**
+	 * Magic method for accessing custom fields
+	 *
+	 * @since 3.3.0
+	 */
+	function __get( $key ) {
+		if ( 'id' == $key ) {
+			_deprecated_argument( 'WP_User->id', '2.1', __( 'Use <code>WP_User->ID</code> instead.' ) );
+			return $this->ID;
 		}
 
-		$this->id = $this->ID;
-		$this->for_blog( $blog_id );
+		return $this->data->$key;
 	}
 
 	/**
+	 * Magic method for setting custom fields
+	 *
+	 * @since 3.3.0
+	 */
+	function __set( $key, $value ) {
+		$this->data->$key = $value;
+	}
+
+	/**
 	 * Set up capability object properties.
 	 *
 	 * Will set the value for the 'cap_key' property to current database table
@@ -511,13 +525,16 @@
 	 */
 	function _init_caps( $cap_key = '' ) {
 		global $wpdb;
+
 		if ( empty($cap_key) )
 			$this->cap_key = $wpdb->prefix . 'capabilities';
 		else
 			$this->cap_key = $cap_key;
-		$this->caps = &$this->{$this->cap_key};
+
+		$this->caps = &$this->data->{$this->cap_key};
 		if ( ! is_array( $this->caps ) )
 			$this->caps = array();
+
 		$this->get_role_caps();
 	}
 
@@ -956,10 +973,10 @@
 	case 'add_post_meta':
 		$post = get_post( $args[0] );
 		$post_type_object = get_post_type_object( $post->post_type );
-		$caps = map_meta_cap( $post_type_object->cap->edit_post, $user_id, $post->ID );	
+		$caps = map_meta_cap( $post_type_object->cap->edit_post, $user_id, $post->ID );
 
-		$meta_key = isset( $args[ 1 ] ) ? $args[ 1 ] : false; 
-			
+		$meta_key = isset( $args[ 1 ] ) ? $args[ 1 ] : false;
+
 		if ( $meta_key && has_filter( "auth_post_meta_{$meta_key}" ) ) {
 			$allowed = apply_filters( "auth_post_meta_{$meta_key}", false, $meta_key, $post->ID, $user_id, $cap, $caps );
 			if ( ! $allowed )
@@ -1080,7 +1097,7 @@
 		return false;
 
 	// Create new object to avoid stomping the global current_user.
-	$user = new WP_User( $current_user->id) ;
+	$user = new WP_User( $current_user->ID) ;
 
 	// Set the blog id.  @todo add blog id arg to WP_User constructor?
 	$user->for_blog( $blog_id );
@@ -1225,7 +1242,7 @@
 	else
 		$user = wp_get_current_user();
 
-	if ( empty( $user->id ) )
+	if ( empty( $user->ID ) )
 		return false;
 
 	if ( is_multisite() ) {
Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 18491)
+++ wp-includes/pluggable.php	(working copy)
@@ -783,7 +783,7 @@
 function is_user_logged_in() {
 	$user = wp_get_current_user();
 
-	if ( $user->id == 0 )
+	if ( $user->ID == 0 )
 		return false;
 
 	return true;
@@ -1308,7 +1308,7 @@
  */
 function wp_verify_nonce($nonce, $action = -1) {
 	$user = wp_get_current_user();
-	$uid = (int) $user->id;
+	$uid = (int) $user->ID;
 
 	$i = wp_nonce_tick();
 
@@ -1334,7 +1334,7 @@
  */
 function wp_create_nonce($action = -1) {
 	$user = wp_get_current_user();
-	$uid = (int) $user->id;
+	$uid = (int) $user->ID;
 
 	$i = wp_nonce_tick();
 
Index: wp-admin/users.php
===================================================================
--- wp-admin/users.php	(revision 18491)
+++ wp-admin/users.php	(working copy)
@@ -216,7 +216,7 @@
 	$update = 'remove';
  	foreach ( $userids as $id ) {
 		$id = (int) $id;
-		if ( $id == $current_user->id && !is_super_admin() ) {
+		if ( $id == $current_user->ID && !is_super_admin() ) {
 			$update = 'err_admin_remove';
 			continue;
 		}
@@ -269,7 +269,7 @@
  	foreach ( $userids as $id ) {
 		$id = (int) $id;
  		$user = new WP_User($id);
-		if ( $id == $current_user->id && !is_super_admin() ) {
+		if ( $id == $current_user->ID && !is_super_admin() ) {
 			echo "<li>" . sprintf(__('ID #%1s: %2s <strong>The current user will not be removed.</strong>'), $id, $user->user_login) . "</li>\n";
 		} elseif ( !current_user_can('remove_user', $id) ) {
 			echo "<li>" . sprintf(__('ID #%1s: %2s <strong>You don\'t have permission to remove this user.</strong>'), $id, $user->user_login) . "</li>\n";
Index: wp-admin/includes/deprecated.php
===================================================================
--- wp-admin/includes/deprecated.php	(revision 18491)
+++ wp-admin/includes/deprecated.php	(working copy)
@@ -255,7 +255,7 @@
 
 	if ( ! $user->has_cap($post_type_obj->cap->edit_others_posts) ) {
 		if ( $user->has_cap($post_type_obj->cap->edit_posts) || ! $exclude_zeros )
-			return array($user->id);
+			return array($user->ID);
 		else
 			return array();
 	}
Index: wp-admin/includes/ms.php
===================================================================
--- wp-admin/includes/ms.php	(revision 18491)
+++ wp-admin/includes/ms.php	(working copy)
@@ -250,7 +250,7 @@
 	if ( ! is_object($errors) )
 		$errors = new WP_Error();
 
-	if ( $current_user->id != $_POST['user_id'] )
+	if ( $current_user->ID != $_POST['user_id'] )
 		return false;
 
 	if ( $current_user->user_email != $_POST['email'] ) {
Index: wp-admin/my-sites.php
===================================================================
--- wp-admin/my-sites.php	(revision 18491)
+++ wp-admin/my-sites.php	(working copy)
@@ -17,7 +17,7 @@
 
 $action = isset( $_POST['action'] ) ? $_POST['action'] : 'splash';
 
-$blogs = get_blogs_of_user( $current_user->id );
+$blogs = get_blogs_of_user( $current_user->ID );
 
 if ( empty( $blogs ) )
 	wp_die( __( 'You must be a member of at least one site to use this page.' ) );
@@ -28,7 +28,7 @@
 
 	$blog = get_blog_details( (int) $_POST['primary_blog'] );
 	if ( $blog && isset( $blog->domain ) ) {
-		update_user_option( $current_user->id, 'primary_blog', (int) $_POST['primary_blog'], true );
+		update_user_option( $current_user->ID, 'primary_blog', (int) $_POST['primary_blog'], true );
 		$updated = true;
 	} else {
 		wp_die( __( 'The primary site you chose does not exist.' ) );