After doing a wee bit of research and on friends' recommendations, DH and I signed up for a hypnobirthing class in July (due end October). In advance of the class, the teacher's sent us a copy of the hypnobirthing book and the Rainbow CD, and dear god, it's driving me chuffing insane! The CD especially makes me want to claw my ears off - her accent reminds me of my American MIL, the affirmations seem completely useless to me (I don't want to "remain still and limp" during labour, FFS!), and the imagery in the CD, inviting me to imagine breathing in different coloured mists, made me think of nothing so much as mustard gas in the trenches. 
If this is my initial reaction, would we be wasting our time going to the classes, or are they usually less violence-inspiring than the CD and book?
(NB I'm not saying that hypnobirthing is therefore absurd and useless for everyone - just that this was how I reacted to the recordings.)