Hair is great yeah. Shading is too obvious when it comes too colours. You should pick colours that don't differ that much from each other. Or use the same colour each time, but play with the opacity on each different layer then.
Looks good. Don't forget to outline the lips... then again depends on your style of vectoring.. I usually go for a dark outline on lips, nose, etc.
Shading looks pretty good atm I agree with Neuron on the shading of the lips. Perhaps go for a darker red or something. Doesn't have to be black
Nice vector man, it looks pretty good. If you keep at it, you'll be awesome at this in no time at all. Nice tag as well man, add it to the Fresh entries. Maybe a really trippy background? Like a white and red candy swirl or something totally hallucinogenic.
I do agree that the background is rather plain. Another thing I noticed is that there's a huge triangle in her hair that's unblended.