Well, I for one refuse to get touchy-feely relativistic and say that a singer's poor intonation is irrelevant, or "artistic choice."
At any rate, I'll agree that Astrud is nothing special and suggest that anybody interested in Brazilian female vocals check out, at the very least
Elis Regina
and then add
Joyce
Leny Andrade (amazing jazz chops)
Nana Caymmi (great bolero singer)
Maria Rita, Elis Regina's daughter, just put out her first album, which is excellent.
Joao's post-Astrud wife, Miucha (Bebel's mother & Chico Buarque's sister), is also an excellent singer. She does the English lyrics on the Getz-Gilberto reunion, "Best of Two Worlds" (that's her on the cover).