When I was first learning to administer my home linux, I found some of these magazines very encouraging. Sometimes I did learn useful technical tricks, but I learned most of the technical stuff from linux books. I did learn some valuable stuff from Mick Bauer's column, The Paranoid Penguin, in Linux Journal.
But in any case, I think that the magazines can be a very good way of learning about some of the fun/cool things you might want to try some day. Linux Format is a good choice for this purpose.