Does Plato have anything good to say about poetry in "Republic"?
For Plato, poetry is an "imitation of an imitation", and adults should be concentrating on imitating the forms directly rather than imitating imitations. On the other hand, Plato does mention that poems are important for educating children and discusses how appropriately edifying poems might appear, emphasizing use of diegesis rather than mimesis. Thus Plato does see poems, because of the way they give pleasure and are memorable, as potentially useful in elementary education.
In "Commentary on Plato's Timaeus" by Proclus, Harold Tarrant, and Dirk Baltzly, the authors note that Plato praises Solon's poetry.
Plato admits that poetry gives us pleasure. Otherwise...not much.