Having the ability to add binding behavior to any callable is an incredibly useful feature if one knows how to take advantage of it, but unfortunately, nothing that currently (publicly) exists comes close to filling the gap `instancemethod`s secrecy leaves.

There really isn't anything else to say about it because it's simply amazing at what it does, and publicly exposing it has zero drawback that I could possibly imagine.
Here's a benchmark I just ran 3.6 (can't check 3.7 but shouldn't be significantly different):

if 1:
    from functools import _lru_cache_wrapper, partial
    method = type((lambda:0).__get__(0))
    for cls in object.__subclasses__():
        if cls.__name__ == 'instancemethod':
            instancemethod = cls
            break
    del cls

    class Object:
        lrx = _lru_cache_wrapper(id, 0, 0, tuple)
        imx = instancemethod(id)
        smx = property(partial(method, id))
        fnx = lambda self, f=id: f(self)

>>> ob = Object()
>>> stex.Compare.load_meth_call('ob', '', None, 'lrx', 'imx', 'smx', 'fnx')

    ------------------------------------------------------------------------
    [*] Trial duration: 0.5 seconds
    [*] Num trials: 20
    [*] Verbose: True
    [*] Imports: ('ob',)

    +-------+-----------------------+-------+-------+
    +-INDEX +-INSTRUCTION           + OPARG-+ STACK-+
    +-------------------------------+-------+-------+
    |[   22]  FOR_ITER ------------> (   12)       1|
    |[   24]  STORE_FAST ----------> (    2)       0|
    |[   26]  LOAD_FAST -----------> (    0)       1|
    |[   28]  LOAD_ATTR -----------> (    2)       1|
    |[   30]  CALL_FUNCTION -------> (    0)       1|
    |[   32]  POP_TOP                 -----        0|
    |[   34]  JUMP_ABSOLUTE -------> (   22)       0|
    +-------+-------+-----------+---+-------+-------+---+
    +-STATEMENT     +   NANOSEC-+ NUM LOOPS-+ EACH LOOP-+
    +---------------+-----------+-----------+-----------+
    | "ob.lrx()"  ->   10.000(b)   55_902(k)     179(ns)
    | "ob.imx()"  ->   10.000(b)   80_053(k)     125(ns)
    | "ob.smx()"  ->   10.000(b)   48_040(k)     208(ns)
    | "ob.fnx()"  ->   10.000(b)   42_759(k)     234(ns)