> The unlock operation is the same, so now you have to arbitrarily pick one 
> of the "lockd" and chose release().

That depends on the implementation.  In the three implementations on

    http://en.wikipedia.org/wiki/Readers-writers_problem

the unlock operateration is different for readers and writers.

> Why take a construct which is essentially a lock that can be acquired in two 
> different ways and force people to view it as separate objects?

I don't see why writing

    lock.exclusive.acquire()

really requires a different way of thinking compared to writing

    lock.exclusive_acquire()

or

    lock.acquire_exclusive()