Kind of has a wintery feel to it as if going through Ponyville in the winter time and simply enjoying the area as you complete season themed task for the ponies there and discover more of who are and why friendship is even more magic than you ever though before!! Wow, what a mouthful. I have to say though, this has a mixture of winter and space put into it making it quite interesting to me indeed I think.
However I can also see where you are coming from in which it could possibly be Twilight's theme but also possibly Luna's theme. I wonder what Celestia's theme would sound like anyways.
The synth sounds very calm and for a majority of the song seems to produce both a winter arctic feel and a space feel as well. Almost as if you were watching snow fall to the ground for the very first time and you sit there letting it fall onto your main and possibly wings as you enjoy it and the cold it brings for you to play in.
The bass is calming and provides a great background beat to listen to I think as you go through the song enjoying the winter feel of it all too. The drums sound good and I like the drum roll at the beginning too helping the song pick up the rest and start up as well.
Overall, great theme song for Twilight I think. Tune is very calm and peaceful, I like it, I like it a lot!