I think that the peas are a great festival band they can get the public moving and jumping around. And no Fergy is not a bad thing I think.

Great festival bands:
Dropkick Murphys (moshpit pinkpop)
Kaiser Chiefs (front Central Park)
Blof (multiple festivals)
System of a down (moshpit pinkpop)
Di-rect (multiple festivals)
Nothing but thieves (never live so far)
Imagine Dragons (never live so far)
Queens of the stone age (pinkpop)
Jeugd van Tegenwoordig (on a distance on two festivals)
The Ting Tings (great lowlands performsnce)
Snoop dogg(come in it's snoop.

Can go on and on with this list....