libuv does not provide a way to inspect the POLLUP status bit, so some types of file descriptor cannot provide EOF condition. This causes a unit-test failure.
libuv attempts to invoke a close callback when closing watch handles, even if one is not defined. This causes the next UV::run_once() call after a handle has been closed to always return immediately. This should not cause a problem in practice, but does cause a unit-test failure.
UV does not wrap signal or child-process watch abilities of libuv, so these are currently emulated by the Loop's built-in signal-pipe mechanism. Because of this, signal or child-process watching cannot be shared by both IO::Async and UV-using code at the same time.