She's definitely fantastic, some of my other favorite jazz vocalists are:
Female, classical (not in any particular order) -
Ella Fitzgerald
Billie Holiday
Rosemary Clooney
Nina Simone
Etta Jones
Actually for female artist...there's too many to list
Current artist -
Diana Krall
Madeleine Peyroux
Sophie Milman
Stacey Kent
Male -
Chet Baker (although first time I heard him...I thought it was a chick)
Nat King Cole
I would have to say Nina Simone. Not only could she sing, she played a wicked piano and had incredible chops. Everytime I listen to her, I am so sad I never got to see her perform.
Love Sarah Vaughn, who could vocally front a smokin' hard bop outfit (Julian Adderly's sextet on the classic '...in the land of Hi-Fi') or pull of timeless pop ditties like 'Broken Hearted Melody.'
Ella, Billie...obvious.
One of my other favorites is Betty Carter, whose jazzy pop song, 'Open the Door,' never ceases to slay me. She also did some great stuff with the Ray Bryant Trio that is more classically jazz oriented.
Nina Simone had a really sad and worn sounding voice that I preferred in the pop setting ('Four Women' and 'Either Way I Lose' are awesome).
Ethel Waters could sing her *** off, and Lena Horne's stuff from the 30s and 40s, when she was a beauty without peer, also holds up well all these years later.
Madeleine Peyroux' CDs are wonderful, but if you've ever seen her in concert, she doesn't belong anywhere near this list. Second worst live show I've ever seen -- a wasted Townes van Zandt will likely never be topped for awfulness.
I'll see your wasted Townes and raise you with a Lou Ann Barton so trashed that, not only could she not remember the lyrics to the songs, she couldn't even sit on a stool without falling over or sliding off.