diff --git a/pymongo/son.py b/pymongo/son.py
index 40c275d18..903561527 100644
--- a/pymongo/son.py
+++ b/pymongo/son.py
@@ -22,7 +22,6 @@ import datetime
 import re
 import binascii
 import base64
-from UserDict import DictMixin
 
 import elementtree.ElementTree as ET
 
@@ -32,7 +31,7 @@ from objectid import ObjectId
 from dbref import DBRef
 from errors import UnsupportedTag
 
-class SON(DictMixin):
+class SON(dict):
     """SON data.
 
     A subclass of dict that maintains ordering of keys and provides a few extra
@@ -69,63 +68,130 @@ class SON(DictMixin):
     """
     def __init__(self, data=None, **kwargs):
         self.__keys = []
-        self.__data = {}
-        if data is not None:
-            if hasattr(data, 'items'):
-                items = data.iteritems()
-            else:
-                items = list(data)
-            for item in items:
-                if len(item) != 2:
-                    raise ValueError("sequence elements must have length 2")
-                self.__keys.append(item[0])
-                self.__data[item[0]] = item[1]
-        if kwargs:
-            self.__merge_keys(kwargs.iterkeys())
-            self.update(kwargs)
-
-    def __merge_keys(self, keys):
-        self.__keys.extend(keys)
-        newkeys = {}
-        self.__keys = [newkeys.setdefault(x, x) for x in self.__keys if x not in newkeys]
+        dict.__init__(self)
+        self.update(data)
+        self.update(kwargs)
 
     def __repr__(self):
         result = []
         for key in self.__keys:
-            result.append("(%r, %r)" % (key, self.__data[key]))
+            result.append("(%r, %r)" % (key, self[key]))
         return "SON([%s])" % ", ".join(result)
 
-    def update(self, data=None, **kwargs):
-        if data is not None:
-            if hasattr(data, "iterkeys"):
-                self.__merge_keys(data.iterkeys())
-            else:
-                self.__merge_keys(data.keys())
-            self.__data.update(data)
-        if kwargs:
-            self.update(kwargs)
-
-    def __getitem__(self, key):
-        return self.__data[key]
-
     def __setitem__(self, key, value):
-        if key not in self.__data:
+        if key not in self:
             self.__keys.append(key)
-        self.__data[key] = value
+        dict.__setitem__(self, key, value)
 
     def __delitem__(self, key):
-        del self.__data[key]
         self.__keys.remove(key)
+        dict.__delitem__(self, key)
 
     def keys(self):
         return list(self.__keys)
 
     def copy(self):
         other = SON()
-        other.__data = self.__data.copy()
-        other.__keys = self.__keys[:]
+        other.update(self)
         return other
 
+    # TODO this is all from UserDict.DictMixin. it could probably be made more efficient.
+    # second level definitions support higher levels
+    def __iter__(self):
+        for k in self.keys():
+            yield k
+
+    def has_key(self, key):
+        try:
+            value = self[key]
+        except KeyError:
+            return False
+        return True
+
+    def __contains__(self, key):
+        return self.has_key(key)
+
+    # third level takes advantage of second level definitions
+    def iteritems(self):
+        for k in self:
+            yield (k, self[k])
+
+    def iterkeys(self):
+        return self.__iter__()
+
+    # fourth level uses definitions from lower levels
+    def itervalues(self):
+        for _, v in self.iteritems():
+            yield v
+
+    def values(self):
+        return [v for _, v in self.iteritems()]
+
+    def items(self):
+        return list(self.iteritems())
+
+    def clear(self):
+        for key in self.keys():
+            del self[key]
+
+    def setdefault(self, key, default=None):
+        try:
+            return self[key]
+        except KeyError:
+            self[key] = default
+        return default
+
+    def pop(self, key, *args):
+        if len(args) > 1:
+            raise TypeError, "pop expected at most 2 arguments, got "\
+                              + repr(1 + len(args))
+        try:
+            value = self[key]
+        except KeyError:
+            if args:
+                return args[0]
+            raise
+        del self[key]
+        return value
+
+    def popitem(self):
+        try:
+            k, v = self.iteritems().next()
+        except StopIteration:
+            raise KeyError, 'container is empty'
+        del self[k]
+        return (k, v)
+
+    def update(self, other=None, **kwargs):
+        # Make progressively weaker assumptions about "other"
+        if other is None:
+            pass
+        elif hasattr(other, 'iteritems'):  # iteritems saves memory and lookups
+            for k, v in other.iteritems():
+                self[k] = v
+        elif hasattr(other, 'keys'):
+            for k in other.keys():
+                self[k] = other[k]
+        else:
+            for k, v in other:
+                self[k] = v
+        if kwargs:
+            self.update(kwargs)
+
+    def get(self, key, default=None):
+        try:
+            return self[key]
+        except KeyError:
+            return default
+
+    def __cmp__(self, other):
+        if isinstance(other, SON):
+            return cmp((dict(self.iteritems()), self.keys()), (dict(other.iteritems()), other.keys()))
+        return cmp(dict(self.iteritems()), other)
+
+    def __len__(self):
+        return len(self.keys())
+
     @classmethod
     def from_xml(cls, xml):
         """Create an instance of SON from an xml document.