The patch looks reasonable to me. Bytecode docs need to be changed.  At 
minimum like this:
===================================================================
--- Doc/library/dis.rst (revision 61097)
+++ Doc/library/dis.rst (working copy)
@@ -463,9 +463,9 @@
    address to jump to (which should be a ``FOR_ITER`` instruction).
 
 
-.. opcode:: LIST_APPEND ()
+.. opcode:: LIST_APPEND (i)
 
-   Calls ``list.append(TOS1, TOS)``.  Used to implement list 
comprehensions.
+   Calls ``list.append(TOS[-i], TOS)``.  Used to implement list 
comprehensions.
 
 
 .. opcode:: LOAD_LOCALS ()
========

More explanation on TOS being removed while TOS[-i] (obviously) not may 
be in order.

For py3k similar optimization should be available for dict and set 
comprehensions.

More unit tests will be helpful, particularly for nested iterations such 
as [(x,y,z) for x in s for y in s for z in s].