I had no idea it was such an old band (it was formed in 1999). I had only heard a couple of their newer songs, "Nineteen" and "Love They Say". I gotta listen to their first album!
I listened to so much Tegan & Sara in high school and college. I kind of lost interest when they put out Heartthrob, it just didn’t sound like “them” anymore. But I recently listened to some of their newer stuff. I particularly liked Hey, I’m Just Like You, which I think sounds very much like a natural progression of “old” T+S.