Björn, the guitarist, has said in an interview that it was a crap guitar, barely playable and with a lousy sound. He couldn't stand using it when playing live, but it looked great for the Eurovision event so he used it.
Ilan is right, it was an epic performance. You knew they would win the minute they started playing.
What made Abba special - apart from Benny's and Björn's songwriting skills which matured over time - were the way Frida's and Agnetha's voices gelled into one. It's reallly hard for me too pick out who sings what and I often catch myself being surprised that Agnetha sings lead in a song when it is actually Frida or vice versa. Their svengali producer Stig Andersson said that much of the studio time was devoted to layering the voices in a way to make it sound like that one supernatural voice ("Dancing Queen" being his prime example), but they could also reporduce it live, those two voices are just a natural match. Neither Frida nor Agnetha sound too convincing when without the other on their solo stuff.
