I'm not sure if Foo Fighters count as a guilty pleasure or not. I've liked them since before I knew that the band was led by the drummer from Nirvana. And I don't feel guilty for liking them. So my conclusion would have to be, no, they are not a guilty pleasure.
They like to do something I still like to do when I play music with friends. Perform a kick-ass cover. Especially if it's a kick-ass cover of a tune that might not have kicked ass so much in it's original version.
Here are some of my favourite cover tunes done by Foo Fighters. Here's them covering Wings "Band on the Run", Prince's "Darling Nikki" and Gerry Raferty's "Baker Street".
Their new album Wasting Light is out on April 12 and you can hear "Rope" here. Sounds good to me.