Their song Many of Horror reached number one last week after being covered by X Factor winner Matt Cardle, as renamed hit When We Collide.
But, after refusing point-blank to speak about the talent contest, lead singer Simon Neil admitted that they were pleased to have the recognition.
He said: "As a song writer it is very flattering that someone has chosen to do our song.
"We get lots of people sending us YouTube links to songs they've covered and it's just really nice to be picked."
But drummer Ben Johnston added that he still feels the band haven't quite hit the mainstream. He said: "I'd still like to think of us as being an underground band, even though we're doing bigger gigs like the Hogmanay party - nothing feels different for us."
Simon revealed his new year's resolution for 2011 is to stop biting his finger nails - after vowing to kick the habit for the past 26 years.
Last night's show was the Ayrshire trio's first ever gig scheduled on Hogmanay, and they said they chose Edinburgh because it is one of the biggest in the world.
James Johnston, bassist, said: "It's weird not to drink before the bells, but we've been partying for the past 30 years or so and this is a different kind of fun. We're making up for it afterward."
The headlining slot was the close to a hugely successful year for the Biffy boys, after touring in Australia, Japan, Europe and of course Scotland.
Their platinum-selling album Only Revolutions was nominated for the Mercury Music Prize.
But the lads said 2011 is to be a more chilled-out year, with less time on the road and more spent in the recording studio working on their next album.
The Ayrshire band vowed to scale back a non-stop schedule touring and live performances in 2011 as they prepare new songs for their new album. They said they were honoured to be in the capital.
The Hogmanay performance was their 138th appearance this year, and a coast-to-coast US tour begins in the New Year followed by a planned tour to Africa. Neil said: "It's just been gig after gig. This year we are going to take some time off."