I just finished my first run of Bastion, and after some 13 hours I must say I am delighted by the experience.
Visually and musically speaking, it should be clear to most that Bastion is appealing. But it's also well-served by a profound narration, an engaging storyline and a fun gameplay.
I really liked the fact that each level is narrated, and can be played in around 15-20 minutes. It's like reading a chapter from a great fantasy book, you can feel like you are in another world in as little time as a coffee break. And yeah, once again, the soundtrack is great, that's definitely something you want to listen to from time to time.
Just give it a try, the Bastion won't let you go.