A Few Things to Say
First off, I liked the style the characters were drawn in. A bit simple perhaps, but pleasantly so. Simple isn't necessarily bad. Also, simple implies innocence, which goes very well with the song, I feel. On that same note, the simple backgrounds fit in well, too.
The only thing I can really ding you for is the minimal animation, but it didn't take away from the overall work.
Now, with regards to the song, I'm fairly certain that this is Snow Patrol, and if it does sound different, I believe it's because this is the acoustic guitar version of the song (no drums, electric guitars, or keyboards). If you can find and compare the techno and acoustic versions of Dirty Vegas's "Days Go By," you'll see what I mean.