The big big downside of gravity waves is that they have no dipole radiators - with electric charge you have + and - and that allows very efficient propagation. For gravity there is only one charge ,and this allows only quadrupole radiation - making it extremely awful for transmission.
Yes, but there is no dispersion relation or absorption by the interstellar medium (not directly related to the quadrupole nature, but that which makes a radiation hard to detect also makes it hard to interfere with).
