I have Gentoo running at home I woulldnt say its the hardest infact bar its diffaculty of doing general admin things it has some features like portage (the package managment system for installing software) that make it one of the easiest to use.

ps. for anyone wanteing to try linux i would really recomend knoppix as a boot to try it out and see what you think, it requires no install it runs of ram and has a hell of a lot of software included.