What if a loop doesn't use actual Python sockets? I haven't updated Rose in a 
while, but when I get to it, the Server class won't have socket objects, since 
it doesn't use them, I use pyuv "handles".

AbstractServer is an interface, Server is one implementation. I think the 
contract is that no matter which event loop implementation you use, the thing 
returned by create_server() implements the abstract interface; only some 
specific implementations return a Server instance. If you are using the sockets 
attribute you are restricting yourself to certain event loop implementations -- 
but there are other aspects of the event loop interface that refer to sockets, 
and those may not be implemented. (E.g. create_server() takes an optional sock 
argument.)

So code that wants to be independent from the loop implementation should not 
use the sockets attribute. But that's part of PEP 3156 interop -- there is a 
minimal set of supported interfaces, and extensions for certain platforms 
(subprocesses are also not supported by all loop implementations).

Ok, so the problem is more on the documentation side. I changed the 
documentation to say that create_server() returns a Server object, because 
AbstractServer is not documented and I like adding links to the definition of 
the class.

For the new create_task() method, I mentionned explicitly in the documentation 
that create_task() may return an instance of a subclass of Task instance in 
third-party projects, instead of an instance of Task.

The documentation should mention explain better the concept of 
interface/abstract class in asyncio: document AbstractEventLoop and 
AbstractServer at least.

For example, we can say that create_server() return type is AbstractServer, and 
the default implementation returns a Server object. Or something like that.

See also:
http://bugs.python.org/issue23046#msg232787