If you want to hear one being used for insanely fast playing check out Rusty Cooley, forget the name of the track...maybe 'The Butcher'. It was a real surprise when he started working his way down from E to actually go lower than B, sounds great if used sparingly. Personally, I wouldn't bother unless you looked at the custom Ibanez models, you can get them with either two lower strings or one higher and one lower. The higher string is supposed to break very easily (although - you need a very heavy guage anyway) but I would I love to try that setup. I have an EBMM Petrucci 7 string, the sound is great but to be honest, I think it is better as a rhythm guitar than one for playing lead... i can imagine 8 strings would be pretty difficult to play.