First of all: I love music, especially when it manages to accentuate a scene in a movie/show.
My most favorite song used in QaF is "Weapon" by the Matthew Good Band. You know, from episode 309, that blow job scene right before the 11 o'clock trick arrives at the loft. Right after Stockwell announces Brian as his gay BFF. When I watched the episode for the first time I fell in love with this song instantly. And when the lyrics started "Here by my side, an angel. Here by my side, the devil." they were just perfect for the situation Brian was in at the time with his involvement in the Stockwell campaign. (And I was wondering who the devil and the angel is when it comes to Brian and Justin ... lol)
Also the "Never turn your back on me. Never turn your back on me again.", well, it could be interpreted as Brian's hidden thoughts on his and Justin's reunification.
Wild speculations put aside: I just love this song so much, I still have the intro as the sound notifying me of newly arrived e-mails. And it hasn't left my playlist for three years. Although, whenever the song starts on my MP3-player I'm a bit puzzled who the heck is sending me an e-mail ... lol