and plowing fields ain't such a hoot...

When it comes to vectoring images from MLP, two things I like to see have been done are smooth lines and colour preservation. With the right software, the latter shouldn't be a problem; Pinkie's colours actually strike me more here than in the episode.

As for smooth lines? I don't think you could have traced this better. The area where the mane folds has been done very well, as with the more delicate outlines in the soil.

The functionality of this particular vector isn't really a point for me to judge, as I'm sure someone somewhere will have a good use for this image. After all, it's completely indistinguishable from the same position in the show. Good job!