Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 15714)
+++ wp-includes/functions.php	(working copy)
@@ -4279,10 +4279,12 @@
 	$i = 0;
 	foreach ( $queries as $q ) {
 		$meta_key = isset( $q['key'] ) ? trim( $q['key'] ) : '';
-		$meta_value = isset( $q['value'] ) ? trim( $q['value'] ) : '';
+		$meta_value = isset( $q['value'] ) ? $q['value'] : '';
 		$meta_compare = isset( $q['compare'] ) ? $q['compare'] : '=';
+		$meta_compare = strtoupper( $meta_compare );
+		$numeric = ( isset( $q['numeric'] ) && $q['numeric'] )? '+0':'';
 
-		if ( !in_array( $meta_compare, array( '=', '!=', '>', '>=', '<', '<=', 'like' ) ) )
+		if ( !in_array( $meta_compare, array( '=', '!=', '>', '>=', '<', '<=', 'LIKE', 'IN', 'BETWEEN' ) ) )
 			$meta_compare = '=';
 
 		if ( empty( $meta_key ) && empty( $meta_value ) )
@@ -4299,14 +4301,31 @@
 		if ( !empty( $meta_key ) )
 			$where .= $wpdb->prepare( " AND $alias.meta_key = %s", $meta_key );
 
+		if ( in_array( $meta_compare, array( 'IN', 'BETWEEN' ) ) ) {
+			if ( !is_array( $meta_value ) )
+				$meta_value = preg_split( '/[,\s]+/', $meta_value );
+		} else {
+			$meta_value = trim( $meta_value );
+		}
+
 		if ( empty( $meta_value ) )
 			continue;
 
-		if ( 'like' == $meta_compare ) {
-			$where .= $wpdb->prepare( " AND $alias.meta_value LIKE %s", '%' . like_escape( $meta_value ) . '%' );
+		if ( 'IN' == $meta_compare ) {
+			$meta_field_types = substr( str_repeat( ',%s', count( $meta_value ) ), 1 );
+			$meta_compare_string = "($meta_field_types)";
+			unset( $meta_field_types );
+		} elseif ( 'BETWEEN' == $meta_compare ) {
+			$meta_value = array_slice( $meta_value, 0, 2 );
+			$meta_compare_string = '%s AND %s';
+		} elseif ( 'LIKE' == $meta_compare ) {
+			$meta_value = '%' . like_escape( $meta_value ) . '%';
+			$meta_compare_string = '%s';
 		} else {
-			$where .= $wpdb->prepare( " AND $alias.meta_value $meta_compare %s", $meta_value );
+			$meta_compare_string = '%s';
 		}
+		$where .= $wpdb->prepare( " AND $alias.meta_value{$numeric} {$meta_compare} {$meta_compare_string}", $meta_value );
+		unset($meta_compare_string);
 	}
 
 	return array( $join, $where );