Being perfectly honest, I don't often enjoy fanvids, and my first reaction to the idea of using this song for a Snarry fanvid was OMGWTF?
But also being perfectly honest, this has a rather special, gentle and unique quality. The footage you've used and the way you've edited, coupled with the aged, somewhat querulous nature of dear old Angela's voice somehow worked together really well.
It's not schmoopy, you are actually telling a very strong story here, but it's tempered by the song, while at the same time the song does capture an aspect of the whole Snarry dynamic that is often hard to understand. Snape is a beast to Harry, and while Harry may not be a 'beauty' - he does have a truly innocent, naive aspect that you really do pick up on here.
I was far more moved by this than I expected to be - and in saying that, consider it a compliment on a job very well and unexpectedly achieved. :)