I'm surprised that no one here has mentioned Buzz Feiten's name yet. This was the first place I ever heard his name, and, if I recall correctly, there were a couple people who were total zealots for his method of tuning/altered guitar nut.

I don't remember exactly what the deal was with his tuning system... wait a second, I'll do a quick google search...

Hmmm... here's a list of artists currently using the Buzz Feiten system:

Joe Satriani, Steve Vai, Larry Carlton, Robert Fripp, Adrian Belew, Pete Anderson, Liona Boyd, "Dimebag" Darrell (Pantera), Jennifer Batten (of the Jeff Beck group), Mick Mars, Michael Landau, Tim Pierce, Dean Parks, Jackson Browne, David Crosby, Stu Hamm, Jimmy Haslip

Here's the link to the home page:

http://www.buzzfeiten.com/index.html

The site doesn't really explain what the tuning system is at all, but if I recall correctly, there's something to do with a staggered guitar nut (i.e. the bit by the machine heads). I don't remember if the frets are changed at all; apparently guitars can be retrofitted, but it's not the same as guitars manufactured with the system...