I know I start with this but Awesome Work! OK, let's start. You did a good job on the colors in this piece. I love your lighting and it really sets the mood in the work. Your colors are good and the background is subtle and appealing. The wings are well drawn and I like you detail on the overall work.
What I must comment on are the tails. There's something about them that I find interesting. The tangle obviously shows their relationship in this work (+ 1 to the ship). I also noticed the addition of the feather on Twilight and found it added to the mood. I found that Rainbow Dash's face seems a little off. Her expression is correct and the style as well but something seems a bit off. Well that's only for me at least. Overall this is excellent work.
Alicorn Twilight to me seems a bit overused, but its a great picture. The style used is something i haven't seen before when looking for pictures. I can see love and happiness blooming from this picture. Almost like there could be a story line waiting to be written for the two of them.
I would rate the originality higher if it were a different pony made into an Alicorn or into a different type of pony then they are in the show, but i have seen too many Alicorn Twilight's out there.
As people say, a picture is worth a thousand words, but i see more than that. Heart and soul went into this picture, so continue putting your heart and soul into your art, and you'll go far.