I love this song... I love Ellie Goulding, actually. She's great. I'm a sucker for a good acoustic number, something about music untouched by editing equipment. It's more base and earthy and real. You can tell a real singer from someone manufactured and all studio by how they handle themselves live, and more importantly, just them and a guitar.
Anyway... In the comments someone said she sounds like she had a cold. It's true. I like it, gravelly and such. Plays into my love of everything with quirks.
I recommend buying this single... I've not yet heard the album but it should be good if it's all along this vein.