I think this icon mostly has much of the cute factor that a lot of people like about their icons, and this is coming from somebody who isn't really much for chibi style. The proportions are mostly spot on for a little chibi icon, and the green eyes really do stand out against the yellows and pinks. The color scheme used here is one that definitely tried and definitely works, and I'm always an avid supporter of great color schemes. The only think I can probably nitpick about the colors is that the pink you used for some reason don't have an outline and its general coloring style to be pretty different from the hair. The pinks look like gradients but the hair does not.

We could probably make this cuter though. I find the mouth to be slightly off center, but if we move it a pixel to our left, the face will be more symmeterical. The single-pixel noise you have for your highligths in the eye is also not really prominent enough and I find that making them 2x2 squares adds to this icon quite a bit. If 2x2 is a bit large for your liking, it's possible to use antialiasing tricks to fake a circle of a size smaller than 2x2 but larger than 1x1.

In case you're not aware of this, it seems that a number of paid professional pixel artists like to push a number of rules in pixel art though. People can look at pixel artists who push these rules on others as 'snobs', but at this point in time, I realize that it's usually pushed for very good reason.

A lot of your outlines include single pixel noise. While I can't be entirely sure what your exact thinking behind this was, but we are probably better off leaving our outlines a solid color, but having your outlines shaded according to a light source is perfectly acceptable. There's a rule against single pixels as they have a tendency to make pixel works look messy. This is probably only a big deal with your broken outline right under the chin, but I find that it shows much better workmanship if you just leave out adding single pixel noise inside your outlines. Usually, single pixels don't really add that much aside from being a distraction, so it's better to use single pixel noise only if they stand for a really specific important detail.

The sharp square corners of pixels also appears quite a lot in the hair, and sometimes they can be an unecessary distraction. They may be minor distractions, but they can add up. If you ever get to mastering AA, you should be able to erase the number of sharp corners in the hair, still have it look exactly what you intended, and there will be less distractions from what really matters - I'd say its the eyes that should have the most attention.

Heck, you could even consider antialiasing the outside with a light color if this icon were to only be used on a light background.

However, we can't really learn antialiasing if we don't have a way of knowing how to control the exact curvature of your lines. I can't be sure if you're aware of this, but to our left from the hair accessory, under the cowlick, we have a diagonal line four pixels by size. Then, that line curves downward with a segment of 2, then 4, then 5, then curving back with a 3 then 2. This line will be smoother if we change this to 1-1-1-1-2-3-6 and so on, instead of 1-1-1-1-2-4-5.

Overall, plenty of things were done right, but with some technical know-how, there's the possibility of having something even better than just good.

The colors and contrast look really good! Nice use of hue shifting. ;D

One of the first things I noticed is that your selective outlining doesn't seem to follow it's purpose, which is to make outlines lighter in areas where light is stronger. There's too many random dark areas on these outlines. There's also a random stroke the lightest portion of the hair closest to the eye on the left.

You also appear to sharpen the hair by adding lighter strokes to the outlines wherever they fit. Try instead to do that with a stroke thickness of 2 pixels, otherwise it looks too grainy.

You also have lot's of colors, but you don't take advantage of this by anti-aliasing areas strong enough. You could use some of those darker colors on the hair all over the sprite to help with anti-aliasing.

The lighter potions of your sprite seem to want a darker border to them, so try using the colors from the hair for that.