A room that is not a rectangle or with any parallel surfaces then introduces a whole host of issues in speaker positioning (as each speaker will see a very different set of reflection points). Interesting discussion of this topic in Roy Gregorys experience of his new room
http://www.theaudiobeat.com/blog/wilson_audio_alexx_thors_hammer_2.htm
http://www.theaudiobeat.com/blog/wilson_audio_alexx_thors_hammer_2.htm