She is a complete package, perhaps too complete in some respects. She is a brilliant, highly skilled and charismatic singer, but clearly has personal demons that are likely to kill her, and, or her career way too soon.
Her phrasing, intonation and vocal timbre sometimes remind me of Sarah Vaughn, sometimes of Nina Simone, but, perhaps, most of all Carmen McCrae. Compare Amy's version of "Moody's Mood for Love" from the "Frank" CD (brilliant...BTW) with Carmen's "The Best is Yet to Come" from the "Sarah:Dedicated to You" CD, and, perhaps, you'll see what I mean.
She also writes great songs. They are melodically and rhythmically quirky and startlingly direct emotionally, and have the great melodic hooks that press the infinite repeat button in your brain. Just try to get "You Know I'm No Good" out of your head after hearing it twice.
I knew this chick was amazing 10 seconds after I heard her singing "Rehab" on Leno one night. She also looked like she had just finished sleeping off a 3-day bender. So...catch while you can cause I'm pretty sure she won't see 30.