I'd like to start off by saying that this is great for the first time you've ever vectored something. Lets jump into it.
The first thing I noticed was that some of the outlines are actually fills that have an outline of a slightly different color. This is most noticeable in the Cutie Mark. I noticed that you spent 11 hours on this vector. WOW, that is a lot. I guarantee that you could cut that time in half if not more if you implement power strokes and cloning methods that are now available in Flutterguy317's Ponyscape V0.1. Not only will this save you time but it will eliminate all variance in stroke width (most noticeable in your vector in the tail). The clones will save you time as well and remove most fill errors.
The blur you use in the stars of her magic is quite excellent and a detail that adds to the vector. The gradients you used in the mane and wing are most effective and a job well done. However, you neglected use of gradients in the tail. The way to vectored the fills of the mane is well done, but the way it is done in the tail created several fill errors. The technique you used for the eyes and mouth is good but can also be done with power strokes if you'd like. With the shoes you did an excellent job, however consider converting your stroke to a path to adjust the points rather than changing the miter limit.
All in all I think that you have a great eye for what image would make a great vector but still need development in technique as this is your first vector. I gave you a 4 in Impact because some of the pony anatomy errors detract from the impact the image is trying to make.
I have reviewed this vector in Inkscape and circled stroke errors in red. Anatomy errors in cyan. Fill errors in yellow. Things I found especially strong are noted in Green. Keep in mind that I circled the most noticeable things to me and not every single mistake. [link]
Have a great day. I hope to see more vectors from you in the future.