Frankly, there's little to be improved on. The translations are highly readable, and they benefit from the high qualities I've mentioned in earlier reviews of earlier volumes in the Grene/Lattimore series.
One major thing is lacking--a detailed biography of Euripides, like those present in the volumes on Aeschylus and (I believe) Sophocles. Also, the editors continue to take their reader's knowledge of Greek mythology for granted. The reader should bring a weighty knowledge of Greek history and mythology (including of the Pelopennesian War, since this is Euripides), or be prepared to miss out on a few metaphors.