To start out as I usually do, please don't feel bad that nothing was rated five stars. For me, five stars means there's no possible way something could improve, and I don't think I'll ever see that.
You executed this extremely well. Rarity is recognizable as Rarity instantly, despite your unique take on her--she's seldom drawn "cute," one sees her most often as the epitome of refinement. The Rarity you've drawn here is your own, but she's still faithful to the original. You've come up with something unique and conveyed it to us beautifully. High marks for vision.
High marks for originality, as well. As I mentioned above, this isn't the Rarity to which we're accustomed. She looks downright playful, as if she'd like whomever she's winking at to wrap her up in that fabric and tickle her. (I'm totally not projecting here, shut up. <_<) The original Rarity seems to be "in there," but this isn't her. This is is a fun take on Rarity, and I like it.
The technique looks a bit... unfinished, sketchy. I'm inclined to think this is deliberate on your part, so I don't think it's a lack of skill, but I also don't feel like it's the best fit. I think this would work slightly better with cleaner lines, and more uniformity in color (not counting obvious shading, of course. Particular examples are the end of the roll of fabric, and the variation in shades of white/gray on Rarity's coat in places where shading doesn't seem to be the intent. She looks slightly... sooty. My comments on technique, however, come from someone who cannot draw to save his life--take them with a grain of salt. I still really like this piece, and favorited it before I began the critique. The things I called out are not to my taste, but I'm not prepared to say they're in any way bad, or not well done.
Despite my reservations about how you handled some of the drawing itself, the "D'aww" factor here is quite high, and that IS a form of impact. I don't look at this and dismiss it as another Rarity image, or save it just because It's Rarity and she's smiling. This is a Rarity I'm going to remember, for any number of reasons. She's getting saved because I know I'm going to want to see her again. I hope, in the future, to see this Rarity on Ask Ecstatic Rarity and Sweetie Belle, perhaps hugging her little sis.
I really like this coloring style, it's very rich and organic and looks great when used with the bold dark outline. Whatever you feel is more rewarding or fun is what you should do I think, or perhaps you could somehow use both style depending on the circumstances.