Haven't used gentoo myself but a friend likes it. Last time he installed he spent > 2 days compiling basically the base system.
Here and on kanotix people seem to complain when the install isn't over in 10 minutes flat
The main reason why he prefers gentoo is that when you compile everything specifically for your hardware you get a fast system.
I seriously doubt if I'm ever going to stray far from a debian based distro. Well, ever and ever, who knows what we'll use in 10 years.