What is the benefit of doing -r 777? I'm willing to try this.

My advice to anyone scared of this:
Back up first, then just try it. Good directions are on page 94. Take an afternoon and give it a shot. Make sure you get some sort of linux environment. I tried doing it all from the N900 and a gparted cd, and it was a real pain. It's easier with a ubuntu live cd. I had to try a couple of things twice.