Amigurumi Miku Hatsune

I like:
The obvious creativity of the piece
The time you must have put in it
The iconic dress is perfect
Her hair is very accurate
Cannot forget that leek
You remembered the tattoo
Instantly recognizable
Overall good job

Possible improvements
The sleeve is missing it's technological component
Her pigtails are almost the right length but not quite
Her hair is uneven but that can be overlooked considering the medium
The leek has a discolored spot
There is hair in her jacket
Missing the little pointy bit of her bangs
Her bangs are too long
Her hair is a bit tangled
Her barrette is round and not square

Try
Using a blue button for her eyes instead of black
Doing the rest of her face