"Kathy's Song" is probably my favorite Simon & Garfunkel song - it is a love song that is beautiful in its simplicity, and its lyrics are pure poetry:
"And so you see I have come to doubt
All that I once held as true
I stand alone without beliefs
The only truth I know is you"
(Here is a great read on the meaning of "Kathy's Song")
(Here is my review on Pretty Much Amazing of First Aid Kit's album The Lion's Roar)
Of course, Simon & Garfunkel's soft harmonies lend to the quiet simplicity of the song, making First Aid Kit a natural to do a cover. The female harmonies do good justice to the song.
Take a listen.