My band (Thursday After) also uses Macs. We use a G4 with an external mic to record and then edit in Soundstudio or Soundtrack.
In reality you shouldn't be asking which bands use Macs for their music...you should be asking which bands don't. But still, here's a list of bands I have personally seen with Macs in the studio:
Avril Lavigne
Blink-182
Coldplay
Radiohead
Moby
Beck
Counting Crows
Everclear
Foo Fighters
Matchbox 20
Nine Days
Our Lady Peace
The Used
Third Eye Blind
The White Stripes
Will Smith
Sum 41
Jason Mraz
Dashboard Confessional
Jimmy Eat World
Dido
Pretty much every studio in the world uses a mac for mixing and recording.