I have a subscription to MacWorld, but can't say that I'm particularly impressed with it. It seems like the advertisers get the best reviews for their products and there's very few in-depth tutorials that go beyond the novice level. I find that I just don't get anything out of MacWorld that I wouldn't otherwise find online.
MacLife seems more about flash than substance, with vast areas of the page covered in graphic art and very little in the way of content. I've picked a few up at the Borders, but I find myself just paging through it finding very little of interest.
Perhaps I am spoiled by MaximumPC, which really seems to be a good balance of solid reviews, how-to articles and editorial commentary.
I have yet to see Mac Format at Borders, but I do remember picking up Amiga Format years ago there and always enjoyed it. I'll have to look harder for it - thanks frazm737.