The Wishon site is a good source of info, so is Pat Dempsey's http://www.horsepowergolf.com which has a pretty clear article about why he spines clubs he assembles. He is a long drive champion, brother of the old Baltimore Oriole catcher, and an excellent club maker.
Only so called neutral spining is legal for clubs in USGA R&A sanctioned events. See the rules appendix or the USGA website.
I know Pat, and play clubs that he made for me, including a MARVELOUS driver. If you get out near LA, you should go see him. Nice guy, great clubfitter and DANG but he can hit it a long way.....
i took a backup up driver that was as good as my gamer spined it and could not keep it on the planet.i also tryed it in a set of irons and didn't have very good results,needless to say i took those shafts out.i do know a lot of tour players that swear by it.maybe i just have more LOFT or LESS loft lol