Ubuntu in particular works, but there's a lot of hacking to get it to do so and little issues abound (at least that's my experience).
Anyway, 5 years ago, getting Linux running on a Powerbook was really easy... I would think it would be better now, not worse...
Ubuntu in particular works, but there's a lot of hacking to get it to do so and little issues abound (at least that's my experience).